EP3227474B1 - Component of a turbocharger, combustion engine comprising said turbocharger and manufacturing method for a component of a turbocharger - Google Patents

Description

On the one hand, the invention relates to a component for a turbo device comprising a compressor and a turbine, with a component body consisting at least partially of a titanium-aluminum alloy, in which the titanium-aluminum alloy has a titanium content of 40 at.% To 60 at. -% and an aluminum content of 5 at .-% to 50 at .-%, wherein the component on its component surface at least partially has a protective layer produced by means of a plasma electrolytic oxidation (PEO), wherein the component has a first material recess which has a bearing bore, characterized in that the component has at least one further material recess which configures a cavity located inside the component body in order to reduce the masses of the component to be accelerated, at least one surface of the component bounding the at least one further material recess partly by means of the plasma electrolyte Isch oxidation (PEO) generated protective layer.

The invention further relates to an internal combustion engine with a turbine device, which comprises a compressor and a turbine.

The invention further relates to a method for producing a turbo device component, in particular a component of a turbo device comprising a compressor and a turbine, made of a titanium-aluminum alloy with a titanium content of 40 at.% And up to 60 at. % and with an aluminum content of 5 at.% to 50 at.% or from a titanium-aluminum alloy with a titanium content of 40 at.% to 55 at.% and with an aluminum content from 35 at.% to 50 at.%, wherein an aluminum oxide-containing protective layer is formed on the turbo device component, characterized in that said aluminum oxide-containing protective layer is provided on a surface of the turbine device component concealed by an undercut of the turbine device component is produced.

Generic components are already known from the prior art.

For example, is from the DE 10 2008 059 617 A1 an exhaust gas turbocharger of an internal combustion engine is known, which in the form of a rotor or a rotating impeller part comprises a compressor and a turbine wheel, which are rotatably connected to each other via a shaft. The turbine wheel is in this case made of a titanium aluminide, so a special titanium-aluminum alloy executed. As a result, it is achieved that the rotor can be produced comparatively inexpensively, which is particularly desirable, since such a rotor is a mass product. The disadvantage here, however, that titanium aluminides above about 750 ° C, however, an increasing with increased temperature surface oxidation, which in turn often leads to premature material failure.

This low oxidation resistance, but also the desire to improve both wear and corrosion protection (eg, hot gas corrosion), and to increase the electrical and thermal resistance of this class of materials, has led to numerous efforts to protect surfaces of titanium aluminide components by suitable surface treatment techniques ,

In particular, scientific studies have shown that oxide formation at elevated temperatures results in a complex mixed oxide layer consisting essentially of alumina, titania, nitrides, various alumina precipitates, and intermetallic phases.

In order to avoid or mitigate such disadvantageous oxide formation, methods are already known from the prior art by means of which it is more or less possible to increase the oxidation resistance of components. Essentially, the strategy is to inhibit an activity of oxides which increase rapidly under elevated temperatures, such as the titanium oxide, while at the same time inhibiting the activity or the occurrence of slow-growing oxides, in particular the aluminum oxide, at the direct interface between the component and the surrounding medium, ie the component surface, preferably should be increased.

Here, a distinction can essentially be made between three types of surface protection and, in particular, oxidation protection, namely surface protection, in particular oxidation protection by application layers (type 1), diffusion layers (type 2) and halogen effect layers (type 3).

In the case of the application layers (type 1), the layer material is deposited on the substrate or component surface as part of a coating process. The composite layer produced hereby adheres, for. As by mechanical interlocking, by adhesive forces or by diffusion areas in combined heat treatment.

On the other hand, diffusion layers (type 2) are formed by an enrichment of various elements in the surface edge zone of the component at elevated temperatures. The substances provided for this purpose diffuse into the substrate or component, so that a generally thin, gradual edge zone can be brought about with a composition differing from the substrate.

The third type differs from this conceptually strong and uses the so-called halogen effect (type 3). In the case of such halogen-effect layers, halides are added to the surface of the substrate or of the component at temperatures lower than the starting temperature. Selective aluminum transport via the gas phase (halogen effect) then forms a thin aluminum oxide layer with good diffusion barrier effect during the actual use of the relevant component or through a preceding heat treatment, whereby a good oxidation protection can be provided on the component.

However, most of the previously used methods or methods for producing such layer systems are very expensive because such methods or methods a require a relatively high degree of automation, a vacuum application, a high energy input or the like.

Furthermore, many of these layer systems have a quality that is inadequate for the application. B. in the form of flaking during thermal cycles due to lack of layer adhesion or in the form of a low abrasion resistance or the like noticeable.

For example, as part of the publicly funded project "Oxidation protection coatings for TiAl" (DFG BO 1979 / 13-2, 01.01.2012-31.12.2012), spray coatings for the oxidation protection of titanium aluminide were developed and tested. In this case, however, has proved disadvantageous that such spray coatings tend to flake off due to their high layer thickness and average layer adhesion, especially in cyclic thermal load. Another disadvantage is the process-related high energy input and the necessary automation of the spray head, which in particular complicates the application of geometrically complex parts.

From the publication DE 10 2012 002 284 A1 a turbine wheel made of a titanium aluminide is also known, on or in the surface of which a halide, in particular from the group fluorine, chlorine or bromine, is introduced or introduced, and on the surface of which an oxide layer is formed by the previously described halogen effect as part of a heat treatment , For such an introduction or introduction of halogens z. B. used an ion implantation.

In a cross-method comparison, ion implantation is one of the most effective methods to increase the oxidation resistance of titanium aluminides. However, such ion implantation is a structurally very complex and expensive process. In order to achieve the same or a comparable effectiveness as with respect to ion implantation, but to reduce the process costs, processes have been developed in which halogens are first applied to the surface by means of an exchange or powder packing process and only then, or as in the powder packing in the rule at the same time be enriched by a thermal treatment in the peripheral zone. Both methods offer the possibility of the treatment of complex surfaces and are comparatively more cost effective to accomplish.

So z. B. in the first experiments in a liquid phase dip with dilute HF solution already similar positive results as on implanted samples can be achieved. However, only the basic proof of an increase in the oxidation resistance based on the formation of an aluminum oxide layer has so far been provided.

A disadvantage of dipping and powder packing processes, however, is the time-consuming choice of suitable parameters and the process control. In order to achieve a positive effect on the oxidation resistance, the halide concentrations must move within a relatively well-defined range. If the halogen concentration is too low, the protective aluminum oxide film will not be fully built up, while over-concentration may adversely affect the general corrosion resistance of a titanium aluminide device.

In addition, all methods or processes based on the halogen effect have the disadvantage that the aluminum oxide films formed are only very thin and, in addition to a limited improvement in corrosion resistance, neither provide good wear protection nor have a greater influence on electrical or thermal insulation of the titanium aluminide Effect components.

However, due to the competitive pressure in general and in particular by the requirements of the predominantly medium-sized industry, which deals with the production, further processing or only generally with titanium aluminide products, layer systems are required which meet the requirements of the application areas with regard to oxidation protection, corrosion protection , Wear protection, a thermal or electrical insulation, a thermal resistance, a layer adhesion strength and much more. be fair and at the same time economically feasible.

One possibility of being able to realize such protective layers in accordance with these requirements has been found by so-called conversion layers (type 4), which supplement the abovementioned three types with respect to type 1, type 2 and type 3, this type 4 being used in science and industry Implementation has remained almost unconsidered so far.

In these conversion layers, in contrast to the application layers, a thin to thick protective layer by a reaction of the surrounding the component atmosphere such. As a fluid, in particular a gas, formed with the substrate or with the component material. This means that no additional material is deposited on the surface but the material is converted to the surface itself (conversion).

For example, in a conductive liquid, the proposed formation mechanism may be initiated by an electrical current flow. In this way, thick and therefore technically usable protective layers can be formed as in the case of the application layers (type 1), which, in contrast to these, however, have a significantly higher layer adhesion due to the gradual transition between the substrate and the conversion layer and, furthermore, independent of the sometimes complex contour of the Component are.

In contrast to diffusion and halogen effect layers (type 2 or type 3), conversion layers are less expensive and thicker with comparable oxidation protection, which additionally provides wear and corrosion protection and, under certain circumstances, a certain electrical or thermal insulation effect.

In this context is from the DE 10 2012 218 666 A1 one of the few examples of such a conversion layer for surface protection of a titanium aluminide component known. In the DE 10 2012 218 666 A1 For example, a titanium aluminide component, in particular a turbine wheel of a turbocharger, is subjected to an electrochemical anodization, which builds up a protective layer containing aluminum oxide, so that the component is good is protected from oxidation. Furthermore, it is pointed out that this component is protected according to the previous description with respect to such conversion layers from harmful and undesirable attacks of environmental conditions.

Although a technically usable layer is provided by the electrochemical anodization, which in contrast to the previously mentioned methods or methods is not only inexpensive, but also has other positive properties in addition to the oxidation and wear protection, the usual limitations for this process remain , A disadvantage of such anodization layers is, for example, that the layer produced thereby accordingly has a high pore content due to the process. In this respect, even under optimal process parameters only a limited oxidation protection can be realized, which is usually significantly inferior to the most effective methods, such as ion implantation. Furthermore, as part of the anodization only a limited wear and corrosion protection can be produced. However, one of the biggest disadvantages is a critical rupture and a limited formation of the anodization layer, in particular in the region of edges and sharp transitions, which often leads to a sufficiently good oxidation protection is not given especially at critical component sites.

The invention has the object of further developing generic components or methods for producing related components in order to overcome at least the above-mentioned disadvantages.

Furthermore, the invention is based on the special object of being able to reliably coat even components that are complicated in construction, which have cavities hidden by undercuts which differ from bearing bores, in order to be able to produce a sufficient protective layer even behind such undercuts.

The object of the invention is achieved on the one hand by a component for a turbo device comprising a compressor and a turbine, with a component body consisting at least partially of a titanium-aluminum alloy, in which the titanium-aluminum alloy has a titanium content of 40 at. -% to 60 at .-% and an aluminum content of 5 at .-% to 50 at .-%, wherein the component on its component surface at least partially has a plasma-electrolytic oxidation (PEO) produced protective layer, wherein the component has a first material recess, which embodies a bearing bore, characterized in that the component has at least one further material recess which configures a cavity located within the component body in order to reduce the masses of the component to be accelerated, wherein the at least one further Material recess limiting surface of the component at least partially a medium s the plasma-electrolytic oxidation (PEO) generated protective layer.

Components made of a titanium-aluminum alloy can be particularly advantageously protected by means of the protective layer produced by plasma electrolytic oxidation with an oxidation barrier in the context of the invention.

The procedure of a plasma-electrolytic oxidation, hereinafter also referred to as "PEO" for short, is essentially known from the prior art.

The protective layer produced in the meaning of the invention by means of the plasma-electrolytic oxidation meets in an excellent manner at least the most important requirements in terms of oxidation protection, corrosion protection, wear protection, thermal or electrical insulation, thermal resistance, a layer adhesion or the like of a titanium-aluminum Alloy of manufactured components.

The present layer may in particular be an oxide-ceramic layer which is produced by a corresponding transformation of the base material.

Advantageously, by means of the present protective layer itself, surfaces with an extremely filigree and / or complex geometry can be finished, so that subsequent or final processing is no longer necessary.

The numbers "from to" mentioned here include the respective upper and lower limits.

The term "titanium-aluminum alloy" or synonymously "aluminum-titanium alloy" is characterized in particular by the titanium and aluminum components described above, wherein in particular the material titanium aluminide is thereby covered. Titanium aluminides are widely known from the prior art, so that they are not further explained at this point.

The term "turbocharger" in the context of the invention describes in particular different types of turbochargers, such as an exhaust gas turbocharger, wherein such turbochargers are characterized in that they comprise a compressor and a turbine. Generic turbo devices are widely known from the prior art, so that in the present case on their structure and operation is not discussed in more detail.

Accordingly, the present term "component" covers a variety of fixed and movable components of such a turbo device, which is shown in more detail later.

On the other hand, the object of the invention is a method for producing a turbo device component, in particular a component of a turbo device comprising a compressor and a turbine according to one of the features described here, of a titanium-aluminum alloy with a titanium content of 40 at. % to 60 at.% and with an aluminum content of 5 at.% to 50 at.% or from a titanium-aluminum alloy with a titanium content of 40 at.% to 55 at. % and dissolved with an aluminum content of 35 at .-% to 50 at .-%, wherein at the turbo device component, an aluminum oxide-containing protective layer is produced, wherein the method is characterized in that this aluminum oxide-containing protective layer by means of a plasma Electrolytic oxidation (PEO) is generated, characterized in that said protective layer containing alumina on a concealed by an undercut of the turbine device component surface of Turbineneinrich production component is generated.

The proposed method, in particular thermally highly loaded components of a turbo device procedurally extremely simple and inexpensive to be protected by a suitable protective layer.

Advantageously, in the context of the invention for producing such a protective layer, in particular an oxide-containing protective layer, ie an excellent oxidation barrier, on or on a component made of a titanium-aluminum alloy, a plasma process is used in a conductive medium.

The component made of a titanium-aluminum alloy can also be protected only partially by an excellent oxidation barrier, wherein the protective layer produced here in the context of the invention can also be produced particularly cost-effective on the component.

Titanium aluminide in the sense of the invention is to be understood as meaning, in particular, a titanium-aluminum or aluminum-titanium alloy which has at least titanium and aluminum in the following percentage amount in atomic percent (at.%), Titanium in particular in a range of .gtoreq 38 at.% To ≦ 59 at.% As well as aluminum may also be present in a range from ≥ 35 at.% To ≦ 50 at.% In the component material.

The present method can also be applied to a titanium, magnesium and a gamma titanium aluminide alloy with appropriate adaptation of the process parameters and, if appropriate, a coordinated pretreatment.

Furthermore, areas of the component which are not to be treated by the present protective layer can be protected during the process by an appropriately formed masking.

By suitably selected process parameters, a layer growth can be temporarily controlled or regulated such that different, but also identical, layer thicknesses can be produced on the component.

By virtue of the present protective layer produced by means of a plasma electrolytic oxidation (PEO), it is possible, in particular, to use dynamically rapidly rotating components, such as those used in a turbo device, reliably from a titanium aluminide, as a result of which these dynamically rotating components are weight-tight can also be designed very easily. Thus, turbo devices equipped with such optimized weight-optimized, dynamically rapidly rotating components have a significantly improved response, which in turn enables internal combustion engines equipped with them to be operated more advantageously.

In this respect, the object of the invention is also achieved by an internal combustion engine having a turbo device, which comprises a compressor and a turbine, wherein the internal combustion engine characterized in that the turbo device comprises at least one component according to one of the features described here, since such equipped internal combustion engines operate more effectively ,

Especially in the above-mentioned context, the object of the invention is further comprised of a component of a turbo device comprising a compressor and a turbine, with a component body consisting at least partially of a titanium-aluminum alloy, with a first material recess which configures a bearing bore, which coincides with its Longitudinal extent in the axial direction along a rotational axis of the component extends, the component having at least one of the bearing bore ausgestaltende first Materialausnehmung different further material recess which configures a lying within the component body cavity to reduce the masses of the component to be accelerated.

By means of such an additionally generated cavity, a further weight reduction on the component can be achieved.

Even with geometrically sophisticated cavities, this component can obtain a very good oxidation barrier, especially where a surface of the component bordering at least one further material recess has at least partially a protective layer produced by means of a plasma electrolytic oxidation (PEO).

In particular, such a component which, for example, as dynamically stressed impeller, such. As a compressor or turbine runner is configured, can be particularly easily prepared by the present protective layer and protected from critical oxidation.

This is particularly true when this component is at least partially made of a titanium aluminide and exposed as dynamically stressed component as a hot gas stream, such as an exhaust stream, an internal combustion engine.

Especially in this context, it is advantageous if the titanium-aluminum alloy has a titanium content of 40 at.% To 55 at.% And an aluminum content of 35 at.% To 50 at.%.

Such a titanium-aluminum alloy designed from a Titanaluminid, which are particularly suitable for dynamically stressed or rotationally dynamic moving components of a turbo device, as they allow a particularly easy-built moving component of the turbo device.

It should be explicitly pointed out that the object of the invention in particular of a component of a turbo device comprising a compressor and a turbine, with a component body consisting at least partially of a titanium-aluminum alloy, with a first material recess which configures a bearing bore extends with its longitudinal extent in the axial direction along an axis of rotation of the component, and with at least one further material recess, which is different from the bearing bore ausgestaltende Materialausnehmung, this component being explicitly characterized in that the at least one further material recess defining surface of Component has at least partially a generated by means of a plasma electrolytic oxidation (PEO) protective layer.

The titanium-aluminum alloy of this component preferably has a titanium content of 40 at.% To 55 at.% And an aluminum content of 35 at.% To 50 at.%.

The weight reduction compared to previous high-temperature materials allows the use of titanium aluminides to increase the efficiency in the respective application as well as the potential for saving energy and thus reducing the environmental impact.

In this respect, it is advantageous if the component comprises a rotating impeller part of the compressor and / or the turbine of the turbine device, wherein the component in any cross section along its axis of rotation at least 65% or 80% of contour elements of its component symmetrical to the axis of rotation of the component are configured ,

As already mentioned, in particular for the application of dynamically moving components or components of the turbo device at elevated temperatures, ie temperatures of .gtoreq.300.degree. C., lightweight and oxidation-resistant components are required.

Titanium aluminides in particular have the potential in numerous technical applications because of their low density of about 3.8 g / cm ³ and due to good mechanical properties at temperatures of 450 ° C to 950 ° C about superalloys such as nickel-based alloys (density 8 , 19 g / cm ³ ) and other heat-resistant materials, as high-temperature materials to replace.

Possible applications, particularly due to the low inertia and the high temperature suitability of these materials, particularly moving parts with high power density, such as turbine blades in engines or gas power plants, engine valves, thermal fenders, hot gas fans or turbine or compressor wheels in turbochargers.

In particular, with regard to modern internal combustion engines or internal combustion engines, such. As diesel or gasoline engines, exhaust gas turbochargers are used more frequently especially.

As materials for these applications, only a few high-temperature heat-resistant materials in question, but especially nickel-based alloys.

Targeted further developments of the titanium aluminides mean that, even at elevated temperatures, they now achieve comparable mechanical properties to those of some well-known nickel-based alloys.

Fortunately, the considerably lower density of the titanium aluminides results in a high potential for weight saving and increased efficiency as well as for reducing pollutant emissions, in particular with regard to such exhaust gas turbochargers.

It is understood that the present component can be manufactured differently.

For example, it is advantageous if the component is produced either by a casting process, in particular investment casting, or powder metallurgy, in particular by a metal powder injection molding or by a generative production process, in particular by electron beam sintering or by selective laser melting preferably in final contour or at least near net shape.

Preferably, the surface of the present component partially or completely comprises an oxide-containing protective layer, which is produced by plasma electrolytic oxidation.

The present component can be produced particularly precisely if the final contour is produced by EDM or by electrochemical machining (ECM).

In particular, the fact that the component has at least one of the bearing bore ausausende first material recess different further material recess, which configures a lying within the component body cavity, in particular to be accelerated masses of the component can be significantly reduced. Since in this case during the acceleration of the component less moments of inertia must be overcome, the turbo device as a whole receives a better response.

A preferred embodiment provides in this context that the at least one further material recess is arranged radially further outside relative to the axis of rotation of the component than the first material recess which configures the bearing bore. In this way, particularly favorably placed cavities can be provided within the component or its component body.

It is also expedient if the at least one further material recess is arranged axially at the same height as the first material recess which configures the bearing bore.

It is expedient if the at least one further material recess is a cavity of the component, which is accessible from a side of the component remote from a blade element. This makes it particularly well possible to produce a protective layer generated by means of a plasma electrolytic oxidation within the component, so that the entire surface of the component or its component body, which limits the inner cavity, can be protected by means of an oxidation barrier.

The side of the component facing away from the blade elements in this case describes the rear side of the component, the front side of the component comprising the blade elements of an impeller part of a compressor or of a turbine.

Another preferred embodiment provides that the at least one further material recess is a cavity of the component, which in the axial direction by a Undercut of the component body, in particular of a suspended on the component body hub part is at least partially hidden. This allows a particularly high material savings and thus a high weight reduction can be achieved on the component.

Advantageously, a protective layer, in particular an aluminum oxide-containing protective layer, can be produced by means of the present plasma electrolytic oxidation even on hard-to-reach surface regions of the component, these surface regions being covered by undercuts of the component from the outside.

In this respect, an advantageous variant of the method also provides that this protective layer containing aluminum oxide is produced on a surface of the turbine device component that is hidden by an undercut of the turbine device component.

The component can be produced with particular weight reduction, if the at least one further material recess is a cavity of the component, which at least partially passes through the axis of rotation of the component.

It goes without saying that the present titanium-aluminum alloy or in particular the titanium aluminide can be alloyed differently depending on the area of application of the component.

In this respect, in particular, a favorable titanium aluminide alloy, in addition to other elements of the Periodic Table and any impurities in a respective frequency of ≤ 1 at .-% one or more of the following alloying elements.

For example, the titanium-aluminum alloy niobium, tantalum, tungsten, zirconium and / or molybdenum, each having a content of more than 0 at .-% to 11 at .-% have.

Cumulatively or alternatively, in the titanium-aluminum alloy iron, chromium, vanadium and / or manganese, each having a proportion of more than 0 at .-% to 4 at .-% have.

In addition, the titanium-aluminum alloy may cumulatively or alternatively comprise boron or carbon or silicon each having a content of more than 0 at.% To 1 at.%.

In this case, the sum of the components present in the component corresponds to an amount of ≦ 100 at.%, Whereby the abovementioned compounds can be present within the abovementioned limits in any desired combinations and in each case at least partially together.

By producing such an alumium oxide-containing protective layer can be prevented in particular in a titanium aluminide component that, as for titanium aluminides in the context of a thermal load in particular at high titanium content or low aluminum content of about below 50 at .-% or of 42 at .-% is known to form an excessive proportion of titanium oxide on the surface.

This may be particularly advantageous because, for example, mixed oxide layers with too large a proportion of titanium dioxide are not or only limited diffusion or gas-tight, wherein the component can not be effectively shielded in this case.

For this reason, both the high temperature self-forming oxide layers and the high-level protective layers formed by a surface treatment step, such as titanium dioxide, are not very resistant to oxidation.

As a result, for example, an oxidation of the actually to be protected by the protective layer component, whereby the component may be damaged or even destroyed.

It is thus clear from what has been described above that a protective layer enriched in particular by aluminum oxide can be advantageous in many cases.

It is particularly advantageous that the method underlying the invention, in contrast to all previously presented methods and methods, a relatively thin to thick oxide-containing protective layer in the range of a few microns to several hundred microns on a titanium-aluminum alloy component, especially from a titanium aluminide, can be produced inexpensively. And this is advantageously also possible almost independently of the outer geometry of the component.

In any case, the present oxide-containing protective layer has a good oxidation resistance due to its content of aluminum oxide.

At the same time, it also has extremely good resistance to wear and corrosion as well as the possibility of thermal or electrical insulation of the component.

By way of example, the present protective layer may be so pronounced that the proportion of aluminum oxide is ≥35% by volume.

In a specific application, in accordance with the method on which the invention is based, a component is initially provided which consists at least partially of a titanium aluminide as described below:
Titanium in a range of greater than or equal to 40 at.% To less than or equal to 55 at.%, With aluminum present in a range greater than or equal to 35 at.% To less than or equal to 50 at.%, And wherein Further, niobium, tantalum, tungsten, zirconium or molybdenum in a range of greater than or equal to 0 at .-% to less than or equal to 11 at .-% and iron, chromium, vanadium or manganese in a range of greater than or equal to 0 at % to less than or equal to 4 at.% and boron or carbon or silicon in a range of greater than or equal to 0 at.% to less than or equal to 1 at.%.

The abovementioned compounds can in this case be present within the abovementioned limits in any desired combinations and in each case also at least partially together.

The production of such components is known per se to the person skilled in the art. For example, such components made entirely or partially of titanium aluminide may be formed by, for example, casting methods, e.g. investment casting, or powder metallurgy, e.g. by metal powder injection molding (MIM), or machining, e.g. by milling or turning, are made of appropriate semi-finished products.

It is understood that the protective layer produced by means of a plasma-electrolytic oxidation on a component can be of various shapes, as explained here.

It is particularly advantageous if the protective layer produced comprises an oxide ceramic layer, in particular an Al ₂ O ₃ layer. By means of this oxide ceramic, a particularly well functioning oxidation barrier can be achieved on the present component.

Moreover, it is advantageous if the protective layer resulting from the conversion of the component surface has a thickness of 0.1 to 300 μm, in particular 1 to 10 μm.

In addition to dynamically loaded or rotating components, it is also advantageous in connection with the present invention if the component comprises a component of the compressor and / or the turbine of the turbo device through which the medium flows.

For example, a component to be coated is a housing part through which exhaust gases, coolants, lubricants flow, such as a water-cooled turbine housing part or a compressor housing part. Such components can be further developed by the present protective layer advantageously, as is explicitly explained in particular in the figure description.

In particular, with regard to a component of a turbomachine comprising a compressor and a turbine, wherein the component comprises an at least partially made of a titanium-aluminum alloy has existing component body, and the titanium-aluminum alloy has a titanium content of 40 at .-% to 60 at .-% and an aluminum content of 5 at .-% to 50 at .-%, it is advantageous if the component comprises a component of the compressor and / or turbine of the turbo device through which fluid flows, since such a component or medium can also be advantageously protected by a protective layer produced by plasma electrolytic oxidation and thus further developed.

For the purposes of the present invention, a medium flowing through the component may be, for example, an exhaust gas, a coolant, a lubricant or the like.

In particular, this component may be a housing part of a compressor or a turbine of a correspondingly configured turbo device through which exhaust gases, coolants, lubricants or the like flow.

Especially with a cylinder head integrated, water-cooled integral turbine housing of an exhaust gas turbocharger, the present invention can be used particularly advantageously. This relates in particular to the partial coating of flow-leading inner cross sections of a correspondingly designed housing part such. B. exhaust-carrying or water-carrying internal channels, which are configured by a turbine housing part of a turbo device.

A coating by means of plasma electrolytic oxidation in the region of plane surfaces of a connecting flange of the turbine housing part to a housing of an internal combustion engine is also advantageous.

In addition, a protective layer produced by means of a plasma electrolytic oxidation can also be used excellently for thermal insulation. For example, such a protective layer can be used to insulate cooling water passages of the turbine housing or exhaust passages of the turbine housing.

It is particularly advantageous that the present protective layer is particularly intimately connected to the respective component, which is particularly advantageous in the case of components subjected to high thermal stress, since these are often already subjected to elastic deformation during normal operation of a turbo device. In addition, with the present protective layer thermal stresses between a base material and a related protective layer can be avoided, since the protective layer produced by plasma electrolytic oxidation has almost the same coefficient of expansion as the actual titanium-aluminum alloy from which the component is made ,

In this respect, there is an atomic bond between the base material of the component and the protective layer produced by means of a plasma-electrolytic oxidation, so that unintentional premature release of this protective layer from the base material can be virtually ruled out.

With regard to a specific application with respect to an exhaust gas turbocharger, the present protective layer is advantageous in that less heat energy is removed from exhaust gases via the housing part into the environment, so that behind the turbo device hotter exhaust gases for heating the catalyst are available, whereby this much faster his can reach optimum operating temperature.

Furthermore, in the present case, it is particularly expedient if the component comprises a bearing part, in particular bearing parts of a shaft-hub connection, of the compressor and / or the turbine of the turbo device. For example, surfaces of bearing bodies can be very well protected from mechanical wear with the present protective layer produced by plasma electrolytic oxidation.

In this respect, it is cumulative or alternatively advantageous if the component comprises a bearing part, in particular bearing parts of a shaft-hub connection, of the compressor and / or the turbine of the turbo device. Such components can be further developed by the present layer advantageous.

In the following, a large number of further advantageous variants of the method are described as follows with regard to specific applications.

A related first process variant provides that a used electrolyte contains a silicon-containing compound as electrolyte base in the range of 0-300 g / l and potassium hydroxide (KOH), water glass (Na2SiO3), phosphoric acid (H3PO4), sodium phosphate (Na3PO4), hydrofluoric acid (HF). , Ammonium hydroxide (NH4OH), boric acid (H3BO3), sulfuric acid (H2SO4), zirconium sulfate (ZrSO4), zirconium tungstate (ZrWO4), ammonium fluoride (NH4F), sodium hydrogen phosphate (NaH2PO4), sodium fluoride diammonium hydrogen phosphate (NH4) 2HPO4, urea (CH4N2O), potassium phosphate ( K3PO4), potassium pyrophosphate (K4O7P2), dipotassium phosphate (K2HPO4), sodium aluminate (Na2A12O4 or NaAl (OH) 4), sodium metaaluminate (NaAlO2), sodium fluoride (NaF), potassium fluoride (KF) and sodium hypophosphite (NaH2PO2) in any combination in the range of, respectively 0 - 120 g / L, but smaller in detail than the electrolyte base, and sodium borate (Na2B4O7), ammonium hydrogendifluoride (NH4HF2), potassium fluorotitanate (K2TiF6), potassium hex fluorozirconate (K2ZrF6), EDTA (C10H12CaN2Na2O8) and their salts, e.g. Disodium ethylenediaminetetraacetate (Na2H2EDTA), tetrasodium ethylenediamine tetraacetate (Na4EDTA) or calcium disodium ethylenediamine tetraacetate (CaNa2EDTA), ammonium metavanadate (NH4VO3), disodium molybdate (Na2MoO4), disodium tungstate (Na2Wo4), hydrogen peroxide (H2O2), citric acid (C6H8O7) and glycerol (C3H8O3) in any combination in the range of 0 - 20 g / L, but in detail less than the electrolyte base, and urotropin in the range (0 - 400 g / L).

Furthermore, it is advantageous if a halide-ion-containing electrolyte is used.

A further variant of the method provides that a used electrolyte contains a phosphorus-containing compound as electrolyte base in the range of 0-300 g / l and potassium hydroxide (KOH), water glass (Na2SiO3), phosphoric acid (H3PO4), sodium phosphate (Na3PO4), hydrofluoric acid (HF), ammonium hydroxide (NH4OH), boric acid (H3BO3), sulfuric acid (H2SO4), zirconium sulfate (ZrSO4), zirconium tungstate (ZrWO4), ammonium fluoride (NH4F), sodium hydrogenphosphate (NaH2PO4), sodium fluoride diammonium hydrogenphosphate (NH4) 2HPO4 , Urea (CH4N2O), potassium phosphate (K3PO4), potassium pyrophosphate (K4O7P2), dipotassium phosphate (K2HPO4), sodium aluminate (Na2A12O4 or NaAl (OH) 4), sodium metaaluminate (NaAlO2), sodium fluoride (NaF), potassium fluoride (KF) and sodium hypophosphite (NaH2PO2) in any combination in the range of 0 - 120 g / L, but in particular lower than the electrolyte base, and sodium borate (Na2B4O7), ammonium hydrogendifluoride (NH4HF2), potassium fluorotitanate (K2TiF6), potassium hexafluorozirconate (K2ZrF6), EDTA (C10H12CaN2Na2O8) and their salts, for example disodium ethylenediamine tetraacetate (Na2H2EDTA), tetrasodium ethylenediamine tetraacetate (Na4EDTA) or calcium disodium ethylenediamine tetraacetate (CaNa2EDTA), ammonium metavanadate (NH4VO3), Din atrium molybdenum (Na2MoO4), disodium tungstate (Na2Wo4), hydrogen peroxide (H2O2), citric acid (C6H8O7) and glycerin (C3H8O3) in any combination in the range of 0 - 20 g / L, but in particular lower than the electrolyte base, and urotropin in the quantitative range (0 - 400 g / L).

In addition, it is advantageous if a used electrolyte, an aluminum-containing compound as an electrolyte base in the range of 0 - 300 g / L and potassium hydroxide (KOH), water glass (Na2SiO3), phosphoric acid (H3PO4), sodium phosphate (Na3PO4), hydrofluoric acid (HF ), Ammonium hydroxide (NH4OH), boric acid (H3BO3), sulfuric acid (H2SO4), zirconium sulfate (ZrSO4), zirconium tungstate (ZrWO4), ammonium fluoride (NH4F), sodium hydrogenphosphate (NaH2PO4), sodium fluoride diammonium hydrogenphosphate (NH4) 2HPO4, urea (CH4N2O), potassium phosphate (K3PO4), potassium pyrophosphate (K4O7P2), dipotassium phosphate (K2HPO4), sodium aluminate (Na2A12O4 or NaAl (OH) 4), sodium metaaluminate (NaAlO2), sodium fluoride (NaF), potassium fluoride (KF) and sodium hypophosphite (NaH2PO2) in any combination Amount range of 0 - 120 g / L each, but smaller in detail than the electrolyte base, as well as sodium borate (Na2B4O7), Ammoni-umhydrogendifluorid (NH4HF2), potassium fluorotitanate (K2TiF6), potassium hexafluorozirconate (K2ZrF6), EDTA (C10H12CaN2Na2O8) and their salts, eg disodium ethylenediamine tetraacetate (Na2H2EDTA), tetrasodium ethylenediamine tetraacetate (Na4EDTA) or calcium disodium ethylenediamine tetraacetate (CaNa2EDTA), ammonium metavanadate (NH4VO3), disodium molybdate (Na2MoO4), disodium tungstate (Na2Wo4), hydrogen peroxide (H2O2), citric acid (C6H8O7) and glycerin (C3H8O3) in any combination in the range of 0 - 20 g / L, respectively in particular less than the electrolyte base, and urotropin in the range (0 - 400 g / L).

Another advantageous variant of the method provides that a used electrolyte is a zirconium- or sulfur-containing compound in the range of 0-300 g / l and potassium hydroxide (KOH), water glass (Na2SiO3), phosphoric acid (H3PO4), sodium phosphate (Na3PO4), hydrofluoric acid (HF), ammonium hydroxide (NH4OH), boric acid (H3BO3), sulfuric acid (H2SO4), zirconium sulfate (ZrSO4), zirconium tungstate (ZrWO4), ammonium fluoride (NH4F), sodium hydrogenphosphate (NaH2PO4), sodium fluoride diammonium hydrogenphosphate (NH4) 2HPO4, urea (CH4N2O) , Potassium phosphate (K3PO4), potassium pyrophosphate (K4O7P2), dipotassium phosphate (K2HPO4), sodium aluminate (Na2A12O4 or NaAl (OH) 4), sodium metaaluminate (NaAlO2), sodium fluoride (NaF), potassium fluoride (KF) and sodium hypophosphite (NaH2PO2) in any combination Amount range of 0 - 120 g / L each, but smaller in detail than the electrolyte base, as well as sodium borate (Na2B4O7), ammonium hydrogendifluoride (NH4HF2), potassium fluorotitanate (K2TiF 6), potassium hexafluorozirconate (K2ZrF6), EDTA (C10H12CaN2Na2O8) and salts thereof, eg disodium ethylenediamine tetraacetate (Na2H2EDTA), tetrasodium ethylenediamine tetraacetate (Na4EDTA) or calcium disodium ethylenediamine tetraacetate (CaNa2EDTA), ammonium metavanadate (NH4VO3) , Disodium molybdenum (Na2MoO4), disodium tungstate (Na2Wo4), hydrogen peroxide (H2O2), citric acid (C6H8O7) and glycerine (C3H8O3) in any combination in the range of 0 - 20 g / L, but in particular smaller than the electrolyte base, and Urotropin in the range (0 - 400 g / L) has.

Furthermore, it is advantageous if, for the conversion of the component surface, a constant or temporally alternating direct current in the range of 0.1 mA to 250 A, in particular 10 mA to 120 A or a DC voltage in the range of 10 to 1200 V, in particular from 80 V to 800 V or a DC power in the range of 1 mW to 300 kW, in particular 8 mW to 96 kW is used.

In addition, it is beneficial; if, for the conversion of the component surface, a current, voltage or power-controlled, uni- or bipolar pulse signal in the form of a rectangle, a sawtooth, a trapezoid or a half-wave or a superposition of these with an effective or peak value of 10 to 1200 V, in particular between 80 and 800 V, in voltage-controlled segments as well as from 0.1 mA to 250 A, in particular 10 mA to 120 A, in current-controlled segments as well as 1 mW and 300 kW, in particular between 8 mW and 96 kW, in power-controlled segments with time variable frequencies in the range of 0.01 Hz to 100 kHz, in particular from 0.1 Hz to 10 kHz is used.

In addition, it is expedient if, for the conversion of the component surface, a current-, voltage- or power-controlled, ideal or deformed sinusoidal signal with arbitrary offset RMS or peak value of 10 to 1200 V, in particular between 80 and 800 V, in voltage-controlled segments as well as 0.1 mA up to 250 A, in particular 10 mA to 120 A, in current-controlled segments and of 1 mW and 300 kW, in particular between 8 mW and 96 kW, in power-controlled segments with time-variable frequencies in the range of 0.01 Hz to 100 kHz, in particular from 0.1 Hz to 10 kHz.

It is likewise advantageous if the electrolyte used to convert the component surface has a temperature range from greater than or equal to 0 ° C. to less than or equal to 100 ° C., in particular greater than or equal to 0 ° C. to less than or equal to 70 ° C. It is understood that the features of the solutions described above or in the claims can optionally also be combined in order to implement the presently achievable advantages and effects in a cumulative manner.

Further features, effects and advantages of the present invention will be explained with reference to the appended drawing and the following description, in which exemplary components of a turbo device comprising a compressor and a turbine with an oxidation barrier layer produced by means of a plasma electrolytic oxidation, PEO, and methods for its production and described.

Components which in the individual figures at least substantially coincide with respect to their function may in this case be identified by the same reference symbols, the components not having to be numbered and explained in all the figures.

Figur 1

schematisch Ansichten von bekannten Schutzschichten, wobei diese hinsichtlich der eingangs erläuterten Klassifizierung in drei Typen unterteilt sind, nämlich Typ 1 Auftragsschicht, Typ 2 Diffusionsschicht und Typ 3 Halogeneffekt-Schicht;

Figur 2

schematisch die eingangs bereits erwähnte Erweiterung bzgl. der vorgeschlagenen Klassifizierung der in der Figur 1 gezeigten Typen 1 bis 3 um den weiteren Typ 4 der Konversionsschicht, wobei zu diesem Typ 4 beispielsweise die Anodisation und das diesbezügliche Verfahren zählt;

Figur 3

schematisch eine tabellarische Übersicht an verschiedenen Methoden bzw. Verfahren, welche für einen Oxidationsschutz von Titanaluminiden in Frage kommen und wissenschaftlich untersucht wurden, wobei gemäß der tabellarischen Übersicht ersichtlich ist, dass Konversionsschichten (Typ 4) gemäß der Darstellung nach der Figur 2, wie etwa die Anodisation oder die Plasma-Elektrolytische Oxidation, hierin nicht enthalten sind;

Figur 4

schematisch eine Ansicht einer mittels Transmissionsrasterelektronenmikroskopie (TEM) erstellten Aufnahme einer Anodisationsschicht auf einem Aluminium-Bauteil;

Figur 5

schematisch eine Ansicht einer mittels Rasterelektronenmikroskopie (REM) erstellten Aufnahme einer Plasma-Elektrolytischen-Oxidschicht auf einem Aluminium-Bauteil nach dem hier beschriebenen Verfahren;

Figur 6

schematisch eine Ansicht einer Oberfläche eines Turbinenrades für einen Turbolader nach einer spanenden Bearbeitung;

Figur 7

schematisch eine Ansicht eines möglichen Verfahrensablaufs eines Selectiv Laser Meltings;

Figur 8

schematisch eine Ansicht einer Oberfläche eines Turbinenrades für einen Turbolader nach elektrochemischer Bearbeitung (ECM);

Figur 9

schematisch eine Querschnittsansicht eines ersten Bauteils mit einer durch eine PEO erzeugten Schutzschicht in Gestalt eines ersten Turbinenrades;

Figur 10

schematisch eine perspektivische Vorderansicht eines weiteren Turbinenrades;

Figur 11

schematisch eine Querschnittsansicht eines weiteren Turbinenrades;

Figur 12

schematisch eine weitere Schnittansicht des in der Figur 11 gezeigten Turbinenrades ;

Figur 13

schematisch eine Querschnittsansicht eines weiteren Turbinenrades;

Figur 14

schematisch eine Querschnittsansicht eines Bauteils in Gestalt eines weiteren Turbinenrades ohne eine durch eine PEO erzeugte Schutzschicht;

Figur 15

schematisch eine perspektivische Rückansicht des in der Figur 11 gezeigten Bauteils;

Figur 16

schematisch eine Querschnittsansicht eines Bauteils mit Hohlräumen in Gestalt eines weiteren Turbinenrades, deren Oberflächen eine durch eine PEO erzeugte Schutzschicht aufweisen;

Figur 17

schematisch eine perspektivische Rückansicht des in der Figur 13 gezeigten Bauteils;

Figur 18

schematisch eine Querschnittsansicht eines Bauteils mit Hohlräumen in Gestalt eines anderen Turbinenrades, welche durch eine PEO erzeugte Schutzschicht aufweisen;

Figur 19

schematisch eine perspektivische Rückansicht des in der Figur 15 gezeigten Bauteils;

Figur 20

schematisch eine erste mögliche Anordnung zum Erzeugen einer Schutzschicht durch eine Plasma-Elektrolytische-Oxidation (PEO) an wenigstens einem insbesondere der in den Figuren 9 bis 16 gezeigten Bauteilen;

Figur 21

schematisch eine Ansicht einer weiteren möglichen Anordnung zum Erzeugen einer Schutzschicht mittels einer Plasma-Elektrolytischen-Oxidation (PEO) an wenigstens einem der in den Figuren 9 bis 16 gezeigten Bauteilen;

Figur 22

schematisch eine Ansicht einer weiteren möglichen Anordnung zum Durchführen eines im Sinne der Erfindung ausgestalteten Verfahrens;

Figur 23

schematisch eine Ansicht einer weiteren möglichen Anordnung zum Erzeugen einer Schutzschicht;

Figur 24

schematisch eine Ansicht einer Oberfläche eines nach dem der Erfindung zugrunde liegenden Verfahren behandelten Bauteils aus einem Titanaluminid mittels Rasterelektronenmikroskopie (REM) in mittlerer und hoher Vergrößerung sowie das Spektrum einer Fläche in EDX-Analysen;

Figur 25

schematisch eine Ansicht der in der Figur 24 gezeigten Oberfläche nach einem Brennvorgang von 100 h bei 950 °C;

Figur 26

schematisch eine Ansicht eines Diagramms hinsichtlich einer prozentualen Gewichtszunahme von nach dem vorgeschriebenen Verfahren behandelten Proben gemäß Ausführungsbeispiel 2 bzw. Ausführungsbeispiel 3 aus einer TNM-Titanaluminid-Legierung und einer GE-Titanaluminid-Legierung bei einem Brennvorgang von 10 h bei 1000 °C;

Figur 27

schematisch eine Ansicht eines Diagramms zur Häufigkeitsverteilung der vorhandenen Elemente in einem EDX-Line-Scan entlang eines Querschnitts einer nach vorgeschriebenem Verfahren behandelten Titanaluminidoberfläche nach einem Brennvorgang von 10 h bei 1000 °C;

Figur 28

schematisch eine Seitenansicht eines Bauteils in Gestalt eines Lagerteils mit einer mittels einer Plasma-Elektrolytischen-Oxidation (PEO) erzeugten Schutzschicht;

Figur 29

schematisch eine perspektivische Ansicht des in der Figur 28 gezeigten Bauteils;

Figur 30

schematisch eine Oberflächenschicht des in den Figuren 28 und 29 gezeigten Bauteils im Querschliff mit einer Struktur, welche Reste von Beschichtungskanälen (Röhren, Pfeile) aufweist;

Figur 31

schematisch eine Ansicht einer Oberflächenschicht im Querschnitt mit einer geschlossenen Struktur (geschlossene Röhre), ähnliche einer Struktur, welche durch einen Diffusionsvorgang erzeugbar ist;

Figur 32

schematisch eine perspektivische und teilweise geschnittene Ansicht eines Verdichtergehäuses mit einer mittels einer Plasma-Elektrolytischen-Oxidation auf einer Innen- sowie Außenkontur des Verdichtergehäuses erzeugten Schutzschicht;

Figur 33

schematisch eine Schnittansicht eines Querschliffs des Verdichtergehäusematerials in einem unbeschichteten Zustand;

Figur 34

schematisch eine Schnittansicht eines Querschliffs des Verdichtergehäusematerials in einem beschichteten Zustand;

Figur 35

schematisch eine Schnittansicht eines Querschliffs des Verdichtergehäusematerials aus einem Druckguss in einem unbeschichteten Zustand;

Figur 36

schematisch eine Schnittansicht eines Querschliffs des Verdichtergehäusematerials aus der Figur 36 in einem beschichten Zustand;

Figur 37

schematisch eine Ansicht einer Tabelle hinsichtlich einer chemischen Zusammensetzung einer Gamma-Titanaluminid-Legierung;

Figur 38

schematisch eine Ansicht einer Beschichtungsmethode eines Turbinenrades;

Figur 39

schematisch eine Ansicht eines unbeschichteten Turbinenrades;

Figur 40

schematisch eine alternative Beschichtungsmethode des fertigen Bauteils in Gestalt des in der Figur 39 gezeigten Turbinenrades;

Figur 41

schematisch eine Ansicht des in den Figuren 38 bis 40 gezeigten Turbinenrades hinsichtlich einer daran ausgebildeten Oxidkeramikschicht;

Figur 42

schematisch eine perspektivische Vorderansicht des insbesondere in Figur 41 gezeigten Turbinenrades; und

Figur 43

schematisch eine perspektivische Rückansicht des insbesondere in den Figuren 41 und 42 gezeigten Turbinenrades.

In the drawing show:

FIG. 1

schematically views of known protective layers, which are divided in terms of the above-mentioned classification in three types, namely type 1 application layer, type 2 diffusion layer and type 3 halogen effect layer;

FIG. 2

schematically the extension already mentioned above regarding the proposed classification of in the FIG. 1 types 1 to 3 shown, for example, of the further type 4 of the conversion layer, this type 4 including, for example, the anodization and the process relating thereto;

FIG. 3

schematically a tabular overview of various methods and methods which are eligible for oxidation protection of titanium aluminides in question and have been studied scientifically, it is apparent from the tabular overview that conversion layers (type 4) as shown in the FIG. 2 such as anodization or plasma electrolytic oxidation, are not included herein;

FIG. 4

1 is a schematic view of a transmission electron microscopy (TEM) image of an anodization layer on an aluminum component;

FIG. 5

1 is a schematic view of a scanning electron microscopy (SEM) image of a plasma electrolytic oxide layer on an aluminum component according to the method described herein;

FIG. 6

schematically a view of a surface of a turbine wheel for a turbocharger after a machining operation;

FIG. 7

schematically a view of a possible procedure of a Selectiv laser melting;

FIG. 8

schematically a view of a surface of a turbine wheel for a turbocharger after electrochemical machining (ECM);

FIG. 9

schematically a cross-sectional view of a first component with a protective layer produced by a PEO in the form of a first turbine wheel;

FIG. 10

schematically a front perspective view of another turbine wheel;

FIG. 11

schematically a cross-sectional view of another turbine wheel;

FIG. 12

schematically another sectional view of the in the FIG. 11 shown turbine wheel;

FIG. 13

schematically a cross-sectional view of another turbine wheel;

FIG. 14

schematically a cross-sectional view of a component in the form of another turbine wheel without a protective layer produced by a PEO;

FIG. 15

schematically a perspective rear view of the in the FIG. 11 shown component;

FIG. 16

schematically a cross-sectional view of a component with cavities in the form of another turbine wheel whose surfaces have a protective layer produced by a PEO;

FIG. 17

schematically a perspective rear view of the in the FIG. 13 shown component;

FIG. 18

schematically a cross-sectional view of a component with cavities in the form of another turbine wheel, which have a protective layer produced by a PEO;

FIG. 19

schematically a perspective rear view of the in the FIG. 15 shown component;

FIG. 20

schematically a first possible arrangement for generating a protective layer by a plasma electrolytic oxidation (PEO) at least one in particular in the FIGS. 9 to 16 shown components;

FIG. 21

schematically a view of another possible arrangement for producing a protective layer by means of a plasma electrolytic oxidation (PEO) at least one of the in the FIGS. 9 to 16 shown components;

FIG. 22

schematically a view of another possible arrangement for performing a configured in the context of the invention method;

FIG. 23

schematically a view of another possible arrangement for producing a protective layer;

FIG. 24

schematically a view of a surface of a treated according to the invention underlying the method component of a titanium aluminide by scanning electron microscopy (SEM) in medium and high magnification and the spectrum of a surface in EDX analysis;

FIG. 25

schematically a view of the in the FIG. 24 shown surface after a firing of 100 h at 950 ° C;

FIG. 26

schematically a view of a diagram in terms of a percentage increase in weight of treated according to the prescribed method samples according to Embodiment 2 and Embodiment 3 of a TNM titanium aluminide alloy and a GE titanium aluminide alloy at a firing time of 10 hours at 1000 ° C;

FIG. 27

schematically a view of a diagram of the frequency distribution of the existing elements in an EDX line scan along a cross section of a prescribed process treated titanium aluminide surface after a firing of 10 h at 1000 ° C;

FIG. 28

schematically a side view of a component in the form of a bearing part with a by plasma electrolytic oxidation (PEO) generated protective layer;

FIG. 29

schematically a perspective view of the in the FIG. 28 shown component;

FIG. 30

schematically a surface layer of the in the FIGS. 28 and 29 in transverse section with a structure which has residues of coating channels (tubes, arrows);

FIG. 31

schematically a view of a surface layer in cross section with a closed structure (closed tube), similar to a structure which can be generated by a diffusion process;

FIG. 32

schematically a perspective and partially sectioned view of a compressor housing with a generated by means of a plasma-electrolytic oxidation on an inner and outer contour of the compressor housing protective layer;

FIG. 33

schematically a sectional view of a cross section of the compressor housing material in an uncoated state;

FIG. 34

schematically a sectional view of a cross section of the compressor housing material in a coated state;

FIG. 35

schematically a sectional view of a cross section of the compressor housing material of a die-cast in an uncoated state;

FIG. 36

schematically a sectional view of a cross section of the compressor housing material from the FIG. 36 in a coated state;

FIG. 37

schematically a view of a table with respect to a chemical composition of a gamma titanium aluminide alloy;

Figure 38

schematically a view of a coating method of a turbine wheel;

FIG. 39

schematically a view of an uncoated turbine wheel;

FIG. 40

schematically an alternative coating method of the finished component in the form of in the FIG. 39 shown turbine wheel;

FIG. 41

schematically a view of the in the Figures 38 to 40 shown turbine wheel with respect to an oxide ceramic layer formed thereon;

Figure 42

schematically a front perspective view of the particular in FIG. 41 shown turbine wheel; and

FIG. 43

schematically a perspective rear view of the particular in the FIGS. 41 and 42 shown turbine wheel.

The in the Figures 1 and 2 each shown on a component 1 layer structures 2, 3 and 4 ( FIG. 1 ) as well as 5 ( FIG. 2 ) are already known from the prior art ways to realize a surface or oxidation protection on a component, in particular made of a titanium-aluminum alloy, wherein the layer structure 2, a coating layer (type 1), the layer structure 3, a diffusion layer (type 2) , the layer structure 4 a halogen effect layer (type 3) and beyond the layer structure 5, a conversation layer (type 4) is reflected.

While in the FIG. 1 shown layer structures 2, 3 and 4 are generated substantially by a material deposition on the component surface, the in the FIG. 2 Layer structure 5 shown produced by a conversion of the component material in the region of its surface, whereby a substantially more intimate bonding of the surface or oxidation protection layer to the relevant component 1 is achieved.

That in the FIG. 3 Schemes 10 additionally shown in the prior art illustrate an overview of scientific investigations for the evaluation of various surface treatments for the protection against oxidation, in which the FIG. 2 Type 4, however, not listed, since this type 4 appeared to be less interesting in the art.

As shown by the FIG. 4 a hexagonal honeycomb structure 15 characteristic for the anodization and process-related hexagonal structure 15 can be seen on the receptacle 14 shown there, in the middle of which there is a large approximately round pore 16. Through a pore channel 17 designed in this respect, the material transports required for the layer structure take place during the process, so that the porosity is unavoidable on the one hand and has a high areal proportion, for example, and thus has a poorer corrosion resistance compared to plasma-electrolytic oxide layers.

Compared to the one in the FIG. 4 14 shows the recording shown in FIG FIG. 5 illustrated further picture 19 that the surface 20 is rougher and thicker. Furthermore, it can be seen that the existing pore structure 21, which is theoretically also unavoidable due to the plasma discharges during the process, is disordered on the one hand and that, compared to the anodization layer (FIG. FIG. 4 ) accounts for a significantly lower proportion of space. Due to the layer build-up mechanism (plasma discharges) and the lower porosity, such a layer not only becomes harder and stronger, but also more resistant to corrosion or oxidation.

As shown by the FIG. 6 the surface of a turbine wheel for a turbocharger after machining is shown. Clearly visible are the production-related geometric deviations 3rd and 4th order, such as grooves 25 or grooves, scales and dome 26th

In the context of the present invention, the component 1 can be produced by a generative method, in particular by electron beam sintering or selective laser melting. These processes have only recently become available, since titanium aluminide powders have so far not been processed by generative processes. Only by the temperature of the powder, ie using a preheating, and using inert gases or vacuum to avoid, inter alia, the oxidation of the powder, cracks and high residual stresses can be avoided by thermal gradients and other disadvantages and the necessary energy to completely melt the powder grains be provided by the electron or laser beam. By using one of the aforementioned methods, the components can be produced in final contour or near-net-shape, so that the final contour can be reworked efficiently and in a resource-saving manner by machining, forming, physical or electrochemical processes, as schematically shown in FIG Representation after the FIG. 7 is shown.

With the FIG. 7 Now also the schematic sequence of the Selective Laser Melting is shown. Input variables of the process are, on the one hand, the geometry of the component 1 to be realized, and also the powder 25, from which the component 1 is constructed. In the first step, a component platform 26 is filled with powder 25 and subsequently drawn off with a wiper 27 in order to achieve a uniform surface. Then, a laser 74 moves the component contour in the respective working plane 75 and melts the powder grains along its path, so that they combine to form a solid 76. Thereafter, the entire platform lowers by a certain distance 77 and is filled up again to the edge with powder 25, so that a new level can be built up by the laser 74 and connected to the component 1. This cycle is repeated until the desired workpiece has been built from the lowest to the highest level and the finished component 1 is available.

In the context of a further embodiment, the provided component 1 has a surface which has been produced by electrochemical or spark erosion processing in a liquid medium. By reworking near-net-shape components, which were produced with one of the abovementioned production methods, the final contour of the component is produced efficiently by means of EDM or electrochemical machining (ECM), saving resources as well as material, as shown after FIG. 8 is shown.

The with the FIG. 8 The illustrated illustration shows the surface of a turbine wheel for a turbocharger after electrochemical machining (ECM). It can be clearly seen that manufacturing-related geometry deviations 80 of the 3rd and 4th order are scarcely present, as in the case of the cutting processes. Instead, process-related pits 81 (pitting) are discernible due to the electrochemical removal mechanism. By contrast with the machining process, productivity is not determined by the machinability of the material. Since titanium aluminides are very difficult to machine, the ECM process has higher productivity and better achievable surface quality than other titanium aluminide processing methods. In particular, near-net-shape components, which were produced, for example, by means of selective laser melting, can thus be produced extremely efficiently and save resources and materials.

In the context of a further embodiment, the provided component 1 has the form of an impeller 90, in particular a turbine or compressor wheel, designed for a rotational movement. That is, it has, with respect to the contour elements in the cross-sectional area along its axis of rotation 91 predominantly, for example, to 65% or 80% or more, an axis symmetry, as shown in FIG FIG. 9 is shown. This illustration shows a cross section of a turbine wheel, for example for a Turbocharger. Due to the design, the turbine wheel predominantly has a symmetry with regard to the contour elements in the cross-sectional area. The symmetry axis corresponds to the axis of rotation 91. Non-symmetrical elements - here due to the curved shape of the blades - are schematically marked by a box 92.

In the context of a further embodiment, the component provided is also a turbine or compressor wheel of a turbocharger (US Pat. FIG. 10 ). As shown by the FIG. 10 schematically a possible embodiment of a turbine wheel for a turbocharger is shown. Evident are the central bore 101 for receiving a shaft and the characteristic curved blades 102 for converting the recovered by the expansion of the hot exhaust gas energy in a rotational movement of the rotor (rotor = composite turbine wheel and shaft).

This according to the representations after FIGS. 11 and 12 schematically a cross-section of another possible embodiment of a turbine wheel for a turbocharger is shown. In this cross section, the solid portions 131 and the hub in the form of an inner bore 132 for receiving a steel shaft (not shown) can be seen. The provided component has a structurally optimized design in the form of a cavity 133 in the component core, which runs rotationally symmetrically between the hub and the blade attachment. This cavity 133 is opened by openings 134 at the bottom or rear of the component, wherein webs 135 remain at right angles.

As shown by the FIG. 13 Again, there is shown schematically a cross section of another possible embodiment of a turbine wheel for a turbocharger. In cross section, the solid portions 141 and the hub in the form of an inner bore 142 for receiving the steel shaft (not shown) can be seen. The provided component has a structure-optimized design in the form of cavities 143 within the blades. Each blade has a small bore 144 on the underside of the blade.

In the context of these further refinements, the component provided, in particular a turbine or compressor wheel, has a structurally optimized shape, in particular a cavity in the component core, which is rotationally symmetrical between the hub and the blade attachment (see also FIG FIGS. 11 and 12 ) and / or within the blades (see in particular FIG. 13 ) on.

This cavity can generally be broken in different planes perpendicular to the axis of rotation of struts or islands of material for stiffening and stabilizing the component.

According to the representations after the FIGS. 14 and 15 another component 301 in the form of an impeller part 302 of a turbine (not shown) of a turbo device (also not shown) is illustrated. The component 301 has a component body 303 made of a titanium-aluminum alloy, which is present as titanium aluminide.

The component 301 has a bearing bore 304 for receiving a shaft part (not shown), wherein the bearing bore 304 extends as a correspondingly formed material recess 305 with its longitudinal extent 306 in the axial direction 307 of the component 301. The bearing bore 304 thus extends in alignment and in the direction of a rotation axis 308 of the component 301.

In order to be able to provide the component 301 as optimally as possible in terms of weight, the component 301 has additional material recesses 310 (numbered only as an example) which configure cavities 311 (numbered only by way of example) within the component body 303 or the component 301.

In this case, the material recess 310 is arranged radially further outward than the bearing bore 304 with respect to the axis of rotation 308 of the component 301.

At least in this exemplary embodiment, the cavities 311 are open from the rear side 312 of the component 301 and thus accessible, wherein the material recess 310 that configures the cavities 311 can be introduced into the component body 303 by different methods.

In this respect, the cavities 311 are accessible from the side 314 facing away from the blade elements 313, namely the rear side 312 of the component 301.

In this respect, the material recess 310 or the respective cavities 311 of this example differ from intermediate spaces 315, which are arranged between the individual blade elements 313 as a result of the design.

In any case, with these additionally created cavities 311, a significant weight reduction is achieved on the component 301, as a result of which the response of a turbo device can be considerably improved.

The component 301 shown here is not provided with a protective layer produced by plasma electrolytic oxidation (PEO).

According to the representations after the FIGS. 16 and 17 another component 401 is also illustrated in the form of an impeller part 402 of a turbine (not shown) of a turbo device (also not shown). The component 401 also has a component body 403 of a titanium-aluminum alloy, which is present as titanium aluminide.

The component 401 has a bearing bore 404 for receiving a shaft part (not shown), wherein the bearing bore 404 extends as a correspondingly formed material recess 405 with its longitudinal extent 406 in the axial direction 407 of the component 401. The bearing bore 404 thus extends in alignment and in the direction of a rotation axis 408 of the component 401.

In order to be able to provide this component 401 as well as possible in terms of weight optimization, it has additional material recesses 410 (numbered only by way of example) which are configured within the component body 403 of the component 401 lying cavities 411 (numbered only as an example).

In this case, the material recesses 410 are arranged radially further outside relative to the axis of rotation 408 of the component 401 than the bearing bore 404.

At least in this exemplary embodiment, the cavities 411 are open from the rear side 412 of the component 401 and thus accessible, wherein the material recess 410 that configures the cavities 411 can be introduced into the component body 403 by different methods.

In this respect, the cavities 411 are accessible from the side 414 facing away from the blade elements 413, namely the back 412 of the component 401.

In this respect, the material recess 410 or the cavities 411 in this case differ from intermediate spaces 415, which are arranged between the individual blade elements 413 as a result of the design.

In any case, with these additionally created cavities 411, a significant weight reduction is achieved on the component 401, as a result of which the response of a turbo device can be considerably improved.

To that in the FIGS. 16 and 17 shown component 401 also in the interior, so in the area of the cavities 411 to equip with an oxidation barrier, the surfaces 420, which limit the cavities 411, provided by a plasma electrolytic oxidation (PEO) protective layer 421 and thus before unintentional, critical signs of wear.

Although the cavities 411 are at least partially hidden by the component body undercuts 422 of the component body 403 in the axial direction 407, all can Regions of the surfaces 420 delimiting the cavities 411 are protected by a protective layer 421 produced by means of plasma electrolytic oxidation (PEO).

The undercuts 422 are limited in this embodiment by the plurality of cross struts 423 (only exemplified).

In the according to the representations of the FIGS. 18 and 19 The component 450 shown is likewise an impeller part 402 of a turbine (not shown) of a turbo device (likewise not shown), wherein the component 401 also again has a component body 403 of a titanium-aluminum alloy, which is present as titanium aluminide.

In order to avoid repetition, only the essential differences between the two components 401 (FIG. FIGS. 16 and 17 ) and 450 ( FIGS. 18 and 19 ) explained. Otherwise, reference is made to the comments on the component 401.

In addition to the features already described with regard to the component 401, the component 450 is characterized in that it has a hub part 451, which is designed in the form of a bearing collar 452. In other words, this hub part 451 is separated from the main body part 453 of the component 450, and is connected to the main body part 453 substantially only by the cross braces 423.

Thus, the undercuts 422 are formed not only by the individual transverse struts 423 but also by the hub portion 451.

A special feature of the component can still be seen in that the cavities 411 of the component 450 in the axial direction 407 by an undercut 422, which are at least partially hidden by the suspended hub portion 451.

Nevertheless, by means of the protective layer 412 produced by the plasma-electrolytic oxidation (PEO), the cavities 411 can be completely and completely coated.

The material recesses 410 in this case form cavities 411 of the component 450, which pass through the axis of rotation 408 of the component 450 and thus also bearing bore 404 at least partially.

In particular, turbochargers come into contact with the hot exhaust gas from the combustion chamber of an internal combustion engine, which is why contacting components of titanium aluminide are particularly exposed to an oxidative attack. As a rule, the turbine wheels made of titanium aluminide are joined together with a steel shaft to form a so-called rotor. Here in particular the with the FIG. 20 The method described below may be advantageous since a protective layer can be formed on the turbine wheel both before the jointing and after the jointing. In the grooved state, the runners can be fixed to the shaft and the turbine wheels partially or completely, in particular up to the joint of steel shaft and turbine wheel, immersed in an electrolyte and acted upon by the connection to a power source with an electric current, as shown FIG. 20 is shown. This illustration shows, in particular, that the rotor, comprising the turbine shaft 112 of titanium aluminide fastened to the steel shaft 111, and a simple ronde-shaped counterelectrode 113 made of stainless steel are introduced into the electrolyte basin 114. The rotor is further immersed in the electrolyte 115 only partially, here up to the joint of steel shaft 111 and turbine wheel 112, so that the steel shaft 111 does not come into contact with the electrolyte 115 and, like the counter electrode 113, is operatively connected to the power source 116 ,

As shown by the FIG. 21 Another possible arrangement for producing a protective layer according to the method described above is described. In this case, the rotor having the turbine shaft 123 made of titanium aluminide attached to the steel shaft 121 and a simple round-shaped counter-electrode 124 made of stainless steel are introduced into the electrolyte tank 125. The rotor is almost completely immersed in the electrolyte 126, wherein the steel shaft 121 is covered with an insulating tape such that the steel shaft 121 does not come into contact with the electrolyte 126 and still is covered beyond the entry point into the electrolyte 126. The component electrode is connected to the power source 127 as well as the counter electrode 124.

By means of the arrangements described herein, a closed, in particular aluminum oxide-rich protective layer can be formed on a turbine wheel made of titanium aluminide in the context of the present invention.

Alternatively, the joint can be covered with a suitable insulating material, for example a polymer, cover film, wax, adhesive tape or similar materials, so that the component with the steel shaft is immersed in the electrolyte until the end of the covered area.

In most cases, the turbine wheel can be used by electrical contacting of the steel shaft as an electrode.

In this way, a dense and durable protective layer is formed on the turbine wheel of the turbocharger, which not only reliably increases the oxidation resistance, but also protects better protection against the otherwise usual in the turbocharger damage effects such as corrosion, dripping and particle impact and abrasion.

Furthermore, production-related disturbance variables such as geometrical deviations in the machining processes or pits or etching pits as in the ECM, or the surface layer as present after the spark erosion, are repaired by the plasma electrolytic conversion and the surface homogenized process-related, so that an intermediate additional cleaning or activation process can be avoided under favorable circumstances.

Further, in this way, other methods for forming a more oxidation-resistant aluminum oxide layer on titanium aluminides, for example, the heat treatment of such composite materials comprising steel, while heating at 800 bis 900 C for 12 to 14 hours in air and thus negative effects on the tempering state of the steel and on the entire component can be avoided.

As shown FIG. 22 schematically another possible, advantageous structure for carrying out the presently described method is shown. Here, the component electrode in the form of a cuboidal component 161 and the counter electrode 162 in the form of a rod made of stainless steel are suspended in the electrolyte 163 in a suitable electrolyte tank 164 and completely covered by this. The two electrodes are electrically connected to a power source 165. For disposal of the resulting process gases or for controlling the temperature of the basin, a suction device 166 and a heat exchanger 167 are provided.

As shown by the FIG. 23 schematically another possible arrangement for generating a protective layer according to the method proposed in the context of the invention is shown. In this case, two turbine wheels 171 and 172 are combined to form one electrode and completely inserted into the electrolyte 173, so that the component electrode and the counter electrode have the identical shape and composition (titanium aluminide).

As shown by the FIG. 24 FIG. 2 shows the surface of a titanium aluminide component treated according to the above-described method by means of scanning electron microscopy (SEM) at medium magnification 181 and high magnification 182 and the spectrum of a flat EDX analysis. It can be seen, in particular, that the pore density and the pore diameter 183 on the titanium aluminide surface, for example, in comparison with a similarly treated aluminum component (see also FIG. 5 ), are atypically low or small. Furthermore, the EDX analysis shows that mixed oxides of titanium and aluminum are expected to form on surface 184.

As shown by the FIG. 25 is the surface area of a titanium aluminide component treated according to the above-described method by means of scanning electron microscopy (SEM) again in medium magnification 191 and high magnification 192 and the spectrum of a surface EDX analysis after a burning process of 100 hours at 950 ° C. It can be seen that the morphology of the surface 193 changes and a closed and compared to the thermally unloaded surface (see, in particular FIG. 24 ) has formed an alumina-rich barrier layer 194.

As shown by the FIG. 26 is the percentage weight gain of samples 201 and 202 treated in accordance with the above-described Embodiment 2 and Embodiment 3, respectively, of a TNM titanium aluminide alloy 203 and a GE titanium aluminide alloy 204 after firing at 1000 for 10 hours ° C reproduced. It becomes clear that both treated samples show a significantly lower weight increase due to oxidation than the untreated reference 205 in both alloys due to the protective layer produced.

As shown by the FIG. 27 By way of example, the frequency distribution of the elements present in the EDX line scan along the cross section of a titanium aluminide surface treated according to the method described above is shown after a firing process of 10 hours at 1000 ° C. Here 211 marks the surface of the formed protective layer and 214 the interface between protective layer and substrate of the approximately 15 μm thick layer. It can be clearly seen that a protective layer with a low proportion of titanium oxide 212 and high aluminum oxide content 213 has formed toward the surface of the component.

At this point it should be noted that for the realization of usually complex geometries, often only one of the aforementioned manufacturing processes, in particular the investment casting, the metal powder injection molding (MIM), the electron beam sintering or the selective laser melting can be used.

In order to produce a protective layer of oxides, in particular with a high proportion of aluminum oxide, on these specific components made of a defined titanium aluminide, the component configured in this way is subjected to an electrochemical plasma treatment by an electric current flow in an aqueous electrolyte. Although this process takes place in a liquid medium, the actual conversion of the surface, i. H. the electrochemical reaction, in the context of short-lived (about 1 micron), high-energy (8000 K) plasma discharges, which screen the surface in all areas in contact with the electrolyte from areas. Such a process may therefore be termed plasma electrolytic oxidation (PEO). In the scientific context, the terms anodization under spark discharge (ANOF), plasma anodization or micro-are oxidation (MAO) are synonymously used for the applied principle.

The method described above is carried out in a controlled manner and furthermore particularly suitable for reliably and completely or partially providing components with a protective layer irrespective of their geometry and size.

In particular, the choice of suitable electrolytes and process parameters, as explained below, may favor the formation of aluminum oxide over the formation of titanium oxide and other oxides of the alloy and / or electrolyte components, so that on the component surface in particular a protective layer rich in aluminum oxide is formed (see FIG. 27 ).

To classify the electrolytes suitable for the plasma electrolytic oxidation, the term "electrolyte base" is used.

In general, and in the following, the term electrolyte base is defined as follows: An electrolyte base is a substance of a class of substances which is most abundant in g / L in addition to water and urotropin in an electrolyte. For example, an electrolyte consisting of 10 g / L Na 2 SiO 3, 4 g / L H 3 PO 4, 2 g / L KOH, and 30 g / L urotropin in demineralized water has a silicate base.

Surprisingly, it has now been found that a titanium aluminide surface is present in a suitable electrolyte comprising a silicon compound, e.g. Sodium waterglass (Na2SiO3), as an electrolyte base under electric current flow through the formation of reaction products of components of the electrolyte and of the substrate in an oxide-containing protective layer, e.g. having alumina, convert.

This is unexpected because usually only pure or low-alloyed aluminum or pure or low-alloyed titanium can be plasma-electrolytically oxidized with the previously known electrolyte compositions. In this case, it is expected that either aluminum or titanium, but not both substances will react in a plasma electrolyte in an identical electrolyte.

Furthermore, it is not expected that a high-alloyed material based on one of the two metals in an electrolyte will even react in this way.

Also surprisingly, it has been found that a titanium aluminide surface is in a suitable electrolyte comprising a phosphorus compound, e.g. Phosphoric acid (H3PO4), as an electrolyte base under electric current flow through the formation of reaction products of components of the electrolyte and the substrate in an oxide-containing protective layer, for. B. alumina, let convert.

This is unexpected because usually only pure or low-alloyed aluminum or pure or low-alloyed titanium can be plasma-electrolytically oxidized with the previously known electrolyte compositions. In this case, it is expected that either aluminum or titanium, but not both substances will react in a plasma electrolyte in an identical electrolyte.

Furthermore, it is not expected that a high-alloyed material based on one of the two metals in an electrolyte will even react in this way.

Also surprisingly, it has been found that a titanium aluminide surface is in a suitable electrolyte comprising an aluminum compound, e.g. Sodium aluminate (Na2A12O4 or NaAl (OH) 4), as an electrolyte base under electric current flow through the formation of reaction products of components of the electrolyte and the substrate in an oxide-containing protective layer, for. B. alumina, let convert.

This is unexpected because usually only pure or low-alloyed aluminum or pure or low-alloyed titanium can be plasma-electrolytically oxidized with the heretofore known electrolyte compositions. In this case, it is expected that either aluminum or titanium, but not both substances will react in a plasma electrolyte in an identical electrolyte.

Furthermore, it is not expected that a high-alloyed material based on one of the two metals in an electrolyte will even react in this way.

Also surprisingly, it has been found that a titanium aluminide surface may be in a suitable electrolyte comprising a zirconium compound, e.g. Zirconium sulfate (ZrSO4) as an electrolyte base under electric current flow by the formation of reaction products of components of the electrolyte and of the substrate in an oxide-containing protective layer, e.g. having alumina, convert.

This is unexpected because usually only pure or low-alloyed aluminum or pure or low-alloyed titanium can be plasma-electrolytically oxidized with the previously known electrolyte compositions. In this case, it is expected that either aluminum or titanium, but not both substances will react in a plasma electrolyte in an identical electrolyte.

Furthermore, it is not expected that a high-alloyed material based on one of the two metals in an electrolyte will even react in this way.

Also surprisingly, it has been found that a titanium aluminide surface is present in a suitable electrolyte comprising a sulfur compound, e.g. Sulfuric acid (H2S04), as an electrolyte base under electric current flow through the formation of reaction products of components of the electrolyte and the substrate in an oxide-containing protective layer, for. B. alumina, let convert.

This is unexpected because usually only pure or low-alloyed aluminum or pure or low-alloyed titanium can be plasma-electrolytically oxidized with the previously known electrolyte compositions. In this case, it is expected that either aluminum or titanium, but not both substances will react in a plasma electrolyte in an identical electrolyte. Furthermore, it is not expected that a high-alloyed material based on one of the two metals in an electrolyte will even react in this way.

In detail, an electrolyte is initially provided, for example in a basin intended for this purpose. This basin may, in addition to the elements listed below for additional process control both a cooling, as well as a circulation and a suction for the process gases ( FIG. 22 ). The particular aqueous electrolyte has one of the above-mentioned electrolyte bases, for example an acid or base of a silicon, phosphorus, aluminum, zirconium or sulfur compound in the quantitative range 0-300 g / l. Particularly preferably, but not necessarily and without any claim to completeness, in addition to one of the aforementioned electrolyte bases, the electrolyte may contain potassium hydroxide (KOH), water glass (Na25iO3), phosphoric acid (H3PO4), sodium phosphate (Na3PO4), hydrofluoric acid (HF), ammonium hydroxide (NH4OH), boric acid (H3B03), sulfuric acid (H2S04), zirconium sulfate (ZrSO4), zirconium tungstate (ZrWO4), ammonium fluoride (NH4F), sodium hydrogen phosphate (NaH2PO4), sodium fluoride dianimonium hydrogen phosphate (N H4) 2H P04, urea (CH4N2O), potassium phosphate (K3P04), potassium pyrophosphate ( K407P2), dipotassium phosphate (K2H PC4), sodium aluminate (N82A1204 or NaAl (OH) 4), sodium metaaluminate (NaA102), Sodium fluoride (NaF), potassium fluoride (KF) and sodium hypophosphite (NaH2PO2) in any combination in the range of 0-120 gIL, but in particular lower than the electrolyte base concentration, and sodium borate (Na2B4O7), ammonium hydrogen difluoride (NH4HF2), potassium fluorotitanate (K2TiF6 ), Potassium hexafluorozirconate (K2ZrF6), EDTA (C10H12CaN2Na2O8) and salts thereof, eg disodium ethylenediamine tetraacetate (Na2H2EDTA), tetrasodium ethylenediamine tetraacetate (NaiEDTA) or calcium disodium ethylenediamine tetraacetate (CaNa2EDTA), ammonium metavanadate (N H4V03) , Disodium molybdenum (Na2MoO4), disodium tungstate (Na2Wo4), hydrogen peroxide (H202), citric acid (C6H807) and glycerine (C3H803) in any combination in the range of 0 - 20 g / L, but in particular lower than the concentration of the electrolyte base, and Urotropin in the range (0 - 400 g / L) have.

In this electrolyte, at least one or more electrically contacted titanium aluminide components are then immersed so as to be completely or partially wetted by the electrolyte. Here, the introduced into the electrolyte components are to be understood as electrodes and are summarized below in any number under the term component electrode.

In a further embodiment, an electrolyte may be used which has halide ions. In particular, the electrolyte may comprise chloride, bromide or fluoride ions. By introducing halide ions into the acidic or basic electrolyte, these halide ions can advantageously be incorporated into the protective layer, thus promoting the formation of a dense aluminum oxide layer, in particular for the protection against oxidation. In particular, a protective layer can be produced in this way, which is predominantly made of aluminum oxide or at least has a high proportion of aluminum oxide, or has a small proportion of titanium dioxide. Thus, the above-described halogen effect (type 3) can be integrated in the context of such a conversion layer (type 4), wherein the advantageous properties of the conversion layer (good wear and corrosion resistance and electrical or thermal insulation) are combined and can be dispensed with at the same time known from the prior art complex processes for ion implantation. In this way, the method in this embodiment is particularly simple and inexpensive, especially in comparison to previously available technologies.

Furthermore, one or more electrodes, for example graphite electrodes or metallic electrodes, as well as titanium aluminide components, may also be introduced into the electrolyte, ie partially or completely submerged, for counter contacting of the component electrode. These are summarized below in any number under the term counter electrode ( FIG. 24 ).

An electrical supply unit with control electronics is also connected to the component and counterelectrode.

In order to convert the component surface into an oxide-rich protective layer, a work is carried out in the following, in particular, between the contacting of the component electrode via the electrolyte and the contacting of the counter electrode. In this case, the component electrode is switched either as an anode or a cathode alternately in a constant or temporally alternating manner, and a DC current or a DC voltage or a DC power is set by the supplying electrical unit, ie. H. By controlling the electrical supply unit is regulated to a defined but temporally variable current or voltage or power value, wherein the component electrode does not change their polarity.

In a further embodiment, this work is done between the contacting of the component electrode and the counter electrode such that the supply unit is regulated to a current, voltage or power controlled pulse signal, ie, a unipolar or bipolar pulse pattern, with each change of polarity the Controlled variable from a current or voltage or power value to a current or Voltage or power can pass. The shape of such a pulse may correspond to a rectangle, a sawtooth, a trapezoid or a half-wave or a superimposition of these and may amount in terms of the RMS or peak value at a voltage setting between 10 to 1200 V, in particular between 80 and 800 V, as well be set freely at a current specification between 0.1 mA to 250 A, in particular 10 mA to 120 A, and at a power specification between 1 mW and 300 kW, in particular between 8 mW and 96 kW, with both effective or peak value, as well as the pauses (pulse off) and pulse times (pulse on) can change with each new pulse during the process. The resulting frequencies between two successive pulses are between 0.01 Hz and 100 kHz, in particular between 0.1 Hz and 10 kHz.

In a further embodiment, this work is done between the contacting of the component electrode and the counter electrode such that the supply unit is regulated to a current, voltage or power controlled sinusoidal signal with any offset in the form of a DC, DC or DC component, ie a wavy pattern, with each change in polarity, the controlled variable from a current or voltage or power value can go to a current or voltage or power value. The shape of such a wave can correspond to an ideal sine or a sine which is deformed by various mathematical operations and can be in terms of magnitude or peak value at a voltage specification between 10 to 1200 V, in particular between 80 and 800 V, and at a current specification between 0.1 mA to 250 A, in particular 10 mA to 120 A, as well as at a power specification between 1 mW and 300 kW, in particular between 8 mW and 96 kW, freely set, with both RMS or peak value, as well as the period of the half wave at can change each new half-wave during the process. The resulting frequencies between two successive pulses are between 0.01 Hz and 100 kHz, in particular between 0.1 Hz and 10 kHz.

In particular, using the mentioned parameter ranges, the formation of an oxidation layer can take place such that a particularly aluminum oxide-rich protective layer grows closed on the component and thus a particularly dense and therefore safe protective layer is formed. The component can be safely and long-term stable protected against external influences such as unwanted oxidation safely used in large series with appropriate quality requirements. In addition, practicable reaction rates can be achieved by using the abovementioned parameter ranges, so that the method is also suitable for series processes, in particular in this refinement.

Here, the applied constant or pulse or waveform current or voltage or power signal is maintained for a predetermined period of time, thus setting a characteristic thickness of the protective layer. Furthermore, a targeted control of the process parameters such as electrolyte temperature, circulation and concentration of individual electrolyte components can help to set suitable reaction conditions and thus a reproducible quality.

Within the scope of a further embodiment, the method described is used such that a layer thickness of the protective layer produced of 0.1 to 300 .mu.m, in particular 1 to 10 .mu.m, is set in a targeted manner by the selection of suitable parameters. In this way, the layer remains elastic and can cause greater stresses, such as those caused by the different thermal expansion coefficients of the component and protective layer, in particular as in thermal load cycles with high heating and cooling rates, for example in the turbocharger, either by a self-elongation or by cracking compensate. In contrast to thick or brittle layers or those which have a poor adhesion to the layer and a clearly definable transition between the substrate and the layer (eg type 1), layer flaking does not occur, which expose entire areas of the component and thus present them leave further oxidation unprotected.

In a further embodiment, the method described in a temperature range of greater than or equal to 0 ° C to less than or equal to 100 ° C, in particular from greater than or equal to 0 ° C to less than or equal to 70 ° C, performed. Such temperature ranges may also have a positive effect on the formation of an aluminum oxide-rich protective layer. Furthermore, the abovementioned temperature ranges are advantageous, in particular for joined attachments of the component, for example in the case of a grooved Stahlanabauteil, which is at least partially made of steel. The relatively low temperature ranges avoid both a negative impact on the structure and the microstructural properties of both the titanium aluminide and the steel.

According to the above method, in which the process of plasma electrolytic oxidation is used, in a defined titanium aluminide current, voltage or power controlled by the surface treatment all or parts of the surface of the component can be selectively oxidized or protected, so that the machined component safely protected against oxidation and thus is particularly long-term stability. Furthermore, the protective layer can be formed without the influence of the geometry of the component, so that the method can be carried out essentially with each component.

As shown by the FIGS. 28 and 29 By way of example, a hub part 550 is shown which, at least in this exemplary embodiment, is completely coated on its surface by a protective layer produced by means of plasma-electrolytic oxidation. Even the illustrated oil inlet holes 551 (only exemplified) are thereby protected, wherein the present protective layer is applied filigree so that a reworking of the hub portion 550 at any surface area of the hub portion is required.

As shown by the FIG. 30 the cross-sectional morphology of the protective layer is shown, here a structure is achieved, which has the remains of coating channels (tubes, see arrow 552). The in the FIG. 31 The morphology shown concerns an anodically produced PEO layer 553.

As shown by the FIG. 31 For example, a morphology of a cathodic PEO layer 554 is shown having a closed structure on the surface which is similar to a structure created by a diffusion process (closed tube).

It is understood that component geometries, in particular those exemplified in the FIGS. 28 and 29 shown oil inlet holes 551, after the production of the present protective layer by means of conventional manufacturing processes can be further processed, such. Grinding, rubbing, honing, lapping, by a superfinishing process or the like.

This generally relates to both outside diameter and inside diameter of a component produced in the sense of the invention.

By means of a suitable process control both variable layer thicknesses and a uniform layer thickness can be produced on the component or on the component.

As shown by the FIG. 32 a turbo device 660 is shown by way of example, on which both inner contours 661 of a compressor 662 and related outer contours 663 are treated or protected by a protective layer produced by plasma electrolytic oxidation.

As a result, the actual component body of the treated component has a kind of sandwich construction, which has the protective layer on both its outer contour 663 and on its inner contour 661, the normal titanium-aluminum alloy being present between these two protective layers.

The turbo device 660 also has a corresponding turbine 664.

As shown by the FIG. 33 For example, the titanium-aluminum alloy is shown in transverse cross-section in an uncoated state.

As shown by the FIG. 34 The sandwich structure is easy to recognize, with the in the FIG. 33 shown material cross section or cross section is shown here in the coated state.

In contrast, according to the representations of the FIGS. 35 and 36 a corresponding material cross section or cross section both in the uncoated state and in the coated state ( FIG. 36 ), wherein the present protective layer is produced here only on the side of the inner contour 661.

For example, the layer thickness of the present protective layer can be produced by selecting different process parameters both as thin layers (50 to 30 μ) and as thick layers (up to 300 μ).

The main advantage of the coating of the present compressor or compressor housing is the fact that the compressor housing is armored. As a result, in particular the dielectric strength of the component is significantly improved, which in turn reduces the risk that in case of failure of a rotating impeller part parts of this impeller part can penetrate the compressor housing.

By means of the present protective layer, it is possible to achieve a layer hardness of from 500 HV to 2000 HV, whereby a component coated in this way experiences a very high resistance to bombardment.

As shown by the FIG. 37 For example, in a table, the chemical composition of a gamma titanium aluminide alloy TMMB-1 is shown by way of example.

It is understood, however, that other light metal alloys, such as the Ti6Al4V titanium alloy, may be used to make the present component.

Further alloys may be, for example, GE 45 22 or GE 48 22 in order to produce in particular a component in the form of a rotating impeller part.

• Gießverfahren (Feinguss) - Ausführung near netshape Geometrie (Schaufelprofil hat Endgeometrie + Aufmaß im Bereich der Außendurchmesser für die nachfolgende Endbearbeitung der Kontur)
• Druckguss - Ausführung near netshape Geometrie (Schaufelprofil hat Endgeometrie + Aufmaß im Bereich der Außendurchmesser für die nachfolgende Endbearbeitung der Kontur)
• Semi-solid-casting Verfahren - Ausführung near netshape Geometrie (Schaufelprofil hat Endgeometrie + Aufmaß im Bereich der Außendurchmesser für die nachfolgende Endbearbeitung der Kontur)
• Thixoforming-Verfahren - Ausführung near netshape Geometrie (Schaufelprofil hat Endgeometrie + Aufmaß im Bereich der Außendurchmesser für die nachfolgende Endbearbeitung der Kontur)
• Gießverfahren (Feinguss) - Ausführung aufgedickte Geometrie im Bereich der Nabe, der Außendurchmesser und der Schaufeldicke (Dickschaufler) + elektrochemische Bearbeitung (ECM) auf die near-netshape Geometrie
• Druckguss - Ausführung aufgedickte Geometrie im Bereich der Nabe, der Außendurchmesser und der Schaufeldicke (Dickschaufler) + elektrochemische Bearbeitung (ECM) auf die near-netshape Geometrie
• Semi-solid-casting - Ausführung aufgedickte Geometrie im Bereich der Nabe, der Außendurchmesser und der Schaufeldicke (Dickschaufler) + elektrochemische Bearbeitung (ECM) auf die near-netshape Geometrie
• Thixoforming-Verfahren - Ausführung aufgedickte Geometrie im Bereich der Nabe, der Außendurchmesser und der Schaufeldicke (Dickschaufler) + elektrochemische Bearbeitung (ECM) auf die near-netshape Geometrie
• auf Basis eines geschmiedeten Rohlings (konventionell oder isotherm geschmiedet, abhängig von der eingesetzten Legierung) und mechanische Bearbeitung mittels Drehen und Fräsen)
• auf Basis eines geschmiedeten Rohlings (konventionell oder isotherm geschmiedet, abhängig von der eingesetzten Legierung) und mechanische Bearbeitung mittels Drehen und Fräsen) auf eine aufgedickte Geometrie (Dickschaufler) + elektrochemische Bearbeitung auf die near-netshape Geometrie
• auf Basis eines geschmiedeten Rohlings (konventionell oder isotherm geschmiedet, abhängig von der eingesetzten Legierung) und elektrochemische Bearbeitung (ECM) auf die near-netshape Geometrie
• SLM-Verfahren (selective laser melting Verfahren) auf Basis eines Metallpulvers aus der entsprechenden Legierung Ausführung aufgedickte Geometrie im Bereich der Nabe, der Außendurchmesser und der Schaufeldicke (Dickschaufler) + elektrochemische Bearbeitung (ECM) auf die near-netshape Geometrie
• EBM-Verfahren (electron beam melting Verfahren) auf Basis eines Metallpulvers aus der entsprechenden Legierung Ausführung aufgedickte Geometrie im Bereich der Nabe, der Außendurchmesser und der Schaufeldicke (Dickschaufler) + elektrochemische Bearbeitung (ECM) auf die near-netshape Geometrie
• MIM Verfahren (metal injection moulding Verfahren) auf Basis eines Metallpulvers aus der entsprechenden Legierung auf eine near-netshape Geometrie
• MIM Verfahren (metal injection moulding Verfahren) auf Basis eines Metallpulvers aus der entsprechenden Legierung - Ausführung aufgedickte Geometrie im Bereich der Nabe, der Außendurchmesser und der Schaufeldicke (Dickschaufler) + elektrochemische Bearbeitung (ECM) auf die near-netshape Geometrie

It goes without saying that a wide variety of production processes can be suitable for the production of the present component, as listed below by way of example:

• Casting (precision casting) - design near netshape geometry (blade profile has final geometry + oversize in the area of the outer diameter for the subsequent finishing of the contour)
• Die casting - design near netshape geometry (blade profile has final geometry + oversize in the area of the outer diameter for the subsequent finishing of the contour)
• Semi-solid-casting process - design near netshape geometry (blade profile has final geometry + allowance in the area of the outer diameter for the subsequent finishing of the contour)
• Thixoforming process - design near netshape geometry (blade profile has final geometry + allowance in the area of the outer diameter for the subsequent finishing of the contour)
• Casting (Investment Casting) - Design of thickened geometry around the hub, outside diameter and blade thickness (Dickschaufler) + electrochemical machining (ECM) on the near-net shape geometry
• Die Casting - Design of thickened geometry around the hub, outside diameter and blade thickness (Dickschaufler) + electrochemical machining (ECM) on the near-net shape geometry
• Semi-solid-casting - Implementation of thickened geometry around the hub, outside diameter and blade thickness (thick shovel) + electrochemical machining (ECM) on the near-net shape geometry
• Thixoforming process - Implementation of thickened geometry around the hub, outside diameter and blade thickness (thick shovel) + electrochemical machining (ECM) on the near-net shape geometry
• based on a forged blank (forged conventionally or isothermally, depending on the alloy used) and mechanical machining by means of turning and milling)
• Based on a forged blank (forged conventionally or isothermally, depending on the alloy used) and mechanical machining by means of turning and milling) on a thickened geometry (Dickschaufler) + electrochemical machining on the near-netshape geometry
• based on a forged blank (conventionally or isothermally forged, depending on the alloy used) and electrochemical machining (ECM) on the near-net shape geometry
• SLM (selective laser melting) process based on a metal powder made from the corresponding alloy Design of thickened geometry in the region of the hub, the outside diameter and the blade thickness (Dickschaufler) + electrochemical machining (ECM) on the near-net shape geometry
• EBM process (electron beam melting process) based on a metal powder made of the corresponding alloy Execution of thickened geometry in the range the hub, outside diameter and blade thickness (Dickschaufler) + electrochemical machining (ECM) on the near-netshape geometry
• MIM process (metal injection molding process) based on a metal powder of the corresponding alloy on a near-net shape geometry
• MIM process (metal injection molding process) based on a metal powder of the corresponding alloy - design thickened geometry around the hub, the outside diameter and the blade thickness (Dickschaufler) + electrochemical machining (ECM) on the near-netshape geometry

• Herstellung des Turbinenradrohteils (near-netshape-Geometrie) nach einem der oben genannten Verfahren
• mechanische Bearbeitung des Turbinenrades = Anbringen der Anbindungsgeometrie (zur Verbindung mit der Welle)
• Keramisieren des Turbinenrades mittels PEO-Verfahren
• Mechanisches (beispielsweise Gewinde) oder stoffliches (Schweißen, Löten, EB-Löten)
• Anbinden des keramisierten Turbinenrades an eine Welle aus einer Stahllegierung bzw.
• aus einer Nickelbasislegierung bzw. in einer weiteren Ausführung an ein Zwischenstück aus einer Nickelbasislegierung
• Fertigbearbeitung des Läufers (beispielsweise Konturschleifen des Läufers und/oder Drehen und Schleifen der Welle)
• Auswuchten des fertigbearbeiteten Läufers
• Optional: nachträgliches PEO-Beschichten

A manufacturing route of the rotor with a ceramized turbine wheel is as follows - ceramifying the turbine wheel before the joint with the shaft

• Production of the turbine wheel blank (near-net shape geometry) according to one of the above-mentioned methods
• mechanical machining of the turbine wheel = attachment of the connection geometry (for connection to the shaft)
• Ceramizing the turbine wheel using the PEO process
• Mechanical (eg thread) or material (welding, soldering, EB-soldering)
• Tying the ceramized turbine wheel to a shaft made of a steel alloy or
• made of a nickel-based alloy or in a further embodiment of an adapter made of a nickel-based alloy
• Finishing of the rotor (eg contour grinding of the rotor and / or turning and grinding of the shaft)
• Balancing the finished rotor
• Optional: subsequent PEO coating

This described embodiment often has the disadvantage that the oxide ceramic layer formed is removed by the finishing (contour grinding turbine wheel) and the balancing and the component is not protected at this point against corrosion and oxidation.

In a downstream coating process, it would be possible to recoat or post-oxidize the removed layer; for this purpose, once again an oxide ceramic layer 699 had to be formed on the component in these regions in which the layer was removed, by means of PEO process or PEO process 698.

The ceramization of the turbine wheel 700 as a single part (without shaft 701 made of steel) could have the advantage that the foreign material of the shaft (for example, a steel alloy) does not adversely affect the oxidation result (see in particular also Figure 38 ).

The contacting of the turbine wheel 700 can take place at different locations.

A possible contacting of the component takes place in a bore 702 in the interior of the turbine wheel.

The bore 702 can be designed as a blind hole 702A or as a through hole.

With a blind hole 702, it should be noted that the hole does not have a negative influence on the strength of the component.

A similar contact also applies to a through hole.

The particular design of the hole can be introduced with a mechanical machining process (turning, milling, grinding, etc.).

In an advantageous embodiment, the bore is already introduced during the production of the blank, for example by a casting method or by the MIM and EBM method.

For better contacting of the component, it is advantageous to rework the hole mechanically once again when it is introduced into the blank. Advantage here: introducing a fit between the turbine wheel and contacting in the bore.

Further areas for contacting would be the area of the wheel back, in a region of the turbine wheel, which is not loaded with regard to oxidation and corrosion to an extent that it comes to damage of the component in operation.

A particularly good contact is ensured by an introduced into the bore or in the blind hole 702 anode member 703.

The oxidation of the turbine shell blank by the PEO process may be performed in a bath 705 using a suitable frame for placing the turbine wheel in the basin 705, a process tuned electrolyte 706, and a corresponding cathode 707 (eg, stainless steel or graphite).

Alternatively, the coating process can also take place in one cell - here, in contrast to the coating in the bath, the electrolyte is supplied to the component.

The component to be coated may be subjected to a pickling process prior to the actual coating process in order to improve the formation of oxide ceramics.

• Herstellung des Turbinenradrohteils (near-netshape-Geometrie) nach einem der oben genannten Verfahren
• Mechanische Bearbeitung des Turbinenrades = Anbringen der Anbindungsgeometrie (zur Verbindung mit der Welle)
• Mechanisches (beispielsweise Gewinde) oder stoffliches (Schweißen, Löten, EB-Löten)
• Anbinden des noch nicht keramisierten Turbinenrades an eine Welle aus einer Stahllegierung bzw. einer Nickelbasislegierung bzw. in einer weiteren Ausführung an ein Zwischenstück aus einer Nickelbasislegierung
• Fertigbearbeitung des Läufers (beispielsweise Konturschleifen des Läufers und/oder Drehen und Schleifen der Welle)
• Auswuchten des fertigbearbeiteten Läufers
• Keramisieren des Turbinenrades mittels PEO-Verfahren

An advantageous manufacturing route of the rotor with a ceramicized turbine wheel is as follows: ceramifying the turbine wheel after the joint with the shaft

• Production of the turbine wheel blank (near-net shape geometry) according to one of the above-mentioned methods
• Mechanical machining of the turbine wheel = attachment of the connection geometry (for connection to the shaft)
• Mechanical (eg thread) or material (welding, soldering, EB-soldering)
• Bonding the not yet ceramized turbine wheel to a shaft made of a steel alloy or a nickel-based alloy or in another embodiment to an intermediate piece of a nickel-based alloy
• Finishing of the rotor (eg contour grinding of the rotor and / or turning and grinding of the shaft)
• Balancing the finished rotor
• Ceramizing the turbine wheel using the PEO process

This embodiment described has the advantage that in this way the areas of the finishing of the turbine wheel (grinding of the outer diameter = contour) and the introduced balancing marks (mechanically or by ECM method) are also ceramized, so that the component is completely protected against corrosion and oxidation.

The oxidation of the impeller in the area of the turbine wheel by means of the PEO process can be carried out in a bath, using a suitable frame for placing the running tool in the pool, a process-matched electrolyte and a corresponding cathode (for example stainless steel or graphite).

The component to be coated (turbine wheel) can be subjected to a pickling process before the actual coating process in order to improve the formation of oxide ceramics.

Areas that are not to be coated / converted / ceramized (for example, the shaft) must be appropriately masked before coating, so that on these protected surfaces no oxide ceramics can form or it comes to damage the surface - for example by a rubber / plastic seal ,

Due to the chemical composition of the light alloy used, the ceramization process will produce a mixed oxide on the turbine wheel (Ti02 and A1203). Problem here is an indefinite oxide growth of Ti02 due to lack of diffusion resistance.

In order to achieve a correspondingly high oxidation protection on the component, it is necessary that a closed A1203 layer is formed.

This is to be achieved in the gamma-TiAl alloy by special parameters by increasing the aluminum activity - it is necessary to reduce the titanium activity (higher reactivity than aluminum).

One possibility is to add aluminum to the electrolyte used or to add silicon to it.

In the case of a turbine wheel made of a titanium alloy, which due to the low aluminum content in the alloy (for example, Ti6AI4V = with 6% aluminum) to a very strong mixed oxide formation with Ti02 excess formation tends, a corresponding Alitierungsverfahren of the component to be coated (turbine) before the actual ceramization process in the PEO process, have a positive influence on the formation of the protective A1203 layer.

The component, in an advantageous embodiment as a finished rotor blade made of a titanium alloy, is alitiert prior to ceramizing with a conventional method in the turbine wheel - it is coated with aluminum or A12O3 layer formers before ceramizing and then in the alitierten area using PEO Process ceramifies to form a layer with A1203 excess. The areas not to be coated (wave) must be masked during alitization as well as during ceramization, so that neither aluminum (alitiation) nor oxide ceramics (ceramizing) can form on these protected surfaces - for example by a rubber / plastic seal - Or kept away from the electrolyte by deliberate immersion in the Keramisierungsbad.

The same applies to the manufacturing route ceramizing the turbine wheel before the joint with the shaft in the area of the connection (if necessary).

In the following, four more concrete exemplary embodiments are described:

Embodiment 1

With regard to a first embodiment, the turbine wheel of a turbocharger rotor is made of a TNM alloy (cf. FIG. 10 ). For this purpose, a titanium aluminide powder of a TNM alloy is first prepared by atomizing and provided for selective laser melting. By means of Selective Laser Melting (see also FIG. 7 ), a turbine wheel is then produced from the atomized powder according to a topology-optimized design. This design can be obtained by means of an algorithm for topology or structure optimization. For this purpose, the real load collective is assumed in a FEM simulation, a cavity in the component core is deposited under certain boundary conditions in the algorithm, and the original design of the turbine wheel is modified while removing material until a weight-optimized Design is achieved with an inner cavity (see. FIGS. 11 and 12 ). This design is implemented by means of selective laser melting with a general allowance of 0.1 mm near the final contour (near-net-shape) in the form of the component. After production, the component is sized with a suitable tool for electrochemical machining in a suitable plant, that is, the allowance is removed to form a high surface quality and so the final contour is produced (see Figure 8). After the ECM process, the component is cleaned and rinsed and without another activation step, such as pickling, for example, in a device according to FIG. 20 given. In this case, the already assembled rotor group consisting of a steel shaft and the attached titanium aluminide turbine wheel is immersed in the electrolyte tank only just below the joint of the rotor, so that the steel shaft does not come into contact with the electrolyte. Subsequently, using a constant-regulated direct current, an aluminum oxide-rich protective layer (cf. FIG. 27 ) generated on the component. Due to the protective layer produced, a closed aluminum oxide layer is already formed in the insert after a short time (cf. FIG. 25 ), which better protects the weight-optimized turbine wheel against particle and droplet impact from the hot exhaust gas and against oxidation compared to an untreated turbine wheel.

Embodiment 2

A titanium aluminide component of a GE 48-2-2 alloy is treated according to the method described above by means of plasma electrolytic oxidation. For this purpose, in each case two identical components as component and counter electrode are completely covered with electrolyte and connected to the power source (see. FIG. 23 ). The electrolyte may be composed as described above. Then, for 20 minutes, a bipolar square-wave pattern controlled at an RMS voltage value of XX is applied at a frequency of 6 Hz, so that there are two components for each electrode alternately sets a positive and then a negative current value based on the applied voltage. In order to dissipate the heat generated by the conversion process and the electrical resistance and to maintain a constant temperature of 18.5 ° C, energy is removed from the process via a heat exchanger. In addition, the electrolyte is circulated via a pumping section and the resulting process gases are discharged via a suction device above the basin. The result is an aluminum oxide-containing protective layer having a thickness of 6 .mu.m to 8 .mu.m , which has a significantly lower tendency to oxidation than the untreated reference and, due to its small layer thickness, a high thermal shock resistance (cf. FIG. 26 ).

Embodiment 3

A titanium aluminide component made of a TNM alloy is treated according to the method described above by means of plasma electrolytic oxidation. For this purpose, a component as a component and a stainless steel blank as a counter electrode in the electrolyte hung and connected to the power source. The component electrode is in this case partially covered by an insulating tape such that the covered area is present both in the electrolyte and outside thereof (cf. FIG. 21 ). The electrolyte may be composed as described above and has, in particular, halides as suggested above. Subsequently, a bipolar sawtooth pattern with a frequency of 2.5 kHz is applied for 15 minutes in such a way that the current remains constant in the electrically positive (anodic) region of the bipolar pattern and in the negative region the voltage remains constant at a suitable peak value of XX A resp XXV. In order to dissipate the heat generated by the conversion process and the electrical resistance and to maintain a constant temperature of 21 ° C, energy is removed from the process via a heat exchanger. In addition, the electrolyte is circulated via a pumping section and the resulting process gases via a suction device derived over the basin. The result is an aluminum oxide-rich protective layer with a thickness of 4 .mu.m to 5 .mu.m , which has a significantly lower tendency to oxidation than the untreated reference and due to their small layer thickness high thermal shock resistance (see. FIG. 26 ).

Embodiment 4

A compressor wheel for an exhaust gas turbocharger made of a 45 XD alloy comprising 45 at.%, 47 at.% Aluminum, 2 at.% Niobium, 2 at.% Manganese and 0.8 at.% TiB 2 is prepared according to the method described above treated plasma electrolytic oxidation. For this purpose, two identical parts each as a component and as a counter electrode is completely hung in the electrolyte and connected to the power source. The electrolyte may be composed as described above. Subsequently, a sinusoidal alternating current with a frequency of 1.5 Hz is applied for 150 minutes such that the regulated current value increases from the beginning to the end of the process from 0 A to a suitable RMS value of XX A, ie passes through a ramp. Furthermore, the sinusoidal current is shifted by an equally ramped DC component (offset) such that the minimum current value in each period is always equal to zero and never becomes negative. In order to dissipate the heat generated by the conversion process and the electrical resistance and to maintain a constant temperature of 65 ° C, energy is extracted from the process via a heat exchanger. In addition, the electrolyte is circulated via a pumping section and the resulting process gases are discharged via a suction device above the basin. The result is a thick, rough and alumina-rich protective layer with a thickness of 250 .mu.m to 280 .mu.m , which has a significantly lower tendency to oxidation than the untreated reference and due to their thickness good wear protection against particle or droplet impact.

It goes without saying that the exemplary embodiments explained above are only first embodiments of the component or method according to the invention. In this respect, the embodiment of the invention is not limited to these embodiments.

Finally, it should be noted here that with regard to chemical names, subscriptions of numbers in the present text can not always be reproduced correctly. However, the expert reads these subscriptions with.

List of reference numbers used:

1

component

2

first layer structure

3

second layer structure

4

third layer construction

5

fourth layer structure

10

schemes

14

admission

15

honeycomb structure

16

pore

17

pore channel

19

further recording

20

surface

21

pore structure

23

grooves

24

Scales, scales, crests

25

powder

26

component platform

27

wiper

74

laser

75

machining plane

76

solid

77

path

80

geometry deviations

81

pitting

90

Wheel

91

axis of rotation

92

box

101

drilling

102

shovel

111

steel shaft

112

turbine

113

counter electrode

114

electrolyte pool

115

electrolyte

116

power source

121

steel shaft

123

turbine

124

counter electrode

125

electrolyte pool

126

electrolyte

127

power source

131

massive areas

132

internal bore

133

cavity

134

breakthroughs

135

Stege

141

massive areas

142

internal bore

143

cavities

144

small hole

161

cuboid component

162

counter electrode

163

electrolyte

164

electrolyte pool

165

power source

166

suction

167

heat exchangers

171

first turbine wheel

172

second turbine wheel

173

electrolyte

181

medium magnification

182

high magnification

183

Pore diameter

184

surface

191

medium magnification

192

high magnification

193

surface

194

Alumina-rich boundary layer

201

first sample

202

second sample

203

TNM titanium aluminide alloy

204

GE titanium aluminide alloy

205

untreated reference

211

surface

212

low proportion of titanium oxide

213

high aluminum oxide content

214

interface

301

component

302

impeller part

303

component body

304

bearing bore

305

material recess

306

longitudinal extension

307

axially

308

axis of rotation

310

material recesses

311

cavities

312

back

313

blade elements

314

opposite side

315

interspaces

401

component

402

impeller part

403

component body

404

bearing bore

405

material recess

406

longitudinal extension

407

axially

408

axis of rotation

410

material recesses

411

cavities

412

back

413

blade elements

414

opposite side

415

interspaces

420

surfaces

421

protective layer

422

undercuts

423

crossbars

450

component

451

hub part

452

bearing sleeve

453

Main component body

550

hub part

551

Oil feed holes

552

arrow

553

PEO-layer

554

another PEO layer

660

Turbo facility

661

inner contours

662

compressor

663

outer contours

664

turbine

665

Aluminum alloy (base material / substrate)

666

Al2O3 layer

698

PEO process

699

oxide ceramic

700

turbine

701

Shaft made of steel

702

drilling

702A

Blind hole

703

anode compartment

705

Bath or basin

706

electrolyte

707

cathode

Claims (25)

1. Component (301) for a turbo device comprising a compressor and a turbine,
   having a component body which consists at least partially of a titanium-aluminium alloy, the titanium-aluminium alloy having a titanium portion of 40 at.% to 60 at.% and an aluminium portion of 5 at.% to 50 at.%,
   the component at least partially having on its component surface a protective layer produced by plasma-electrolytic oxidation (PEO), the component having a first material recess forming a bore for a bearing,
   characterized in that
   the component has at least one additional material recess (310) forming a cavity (311) inside the component body so as to reduce the accelerating masses of the component,
   a surface of the component which delimits the at least one additional material recess at least partly having a protective layer produced by means of said plasma-electrolytic oxidation (PEO).
2. Component according to Claim 1, characterized in that the component comprises a component of the compressor and/or of the turbine of the turbo device through which a medium flows; in particular, a housing component through which exhaust gases, coolants, lubricants flow; such as a water-cooled turbine housing component or a compressor housing component.
3. Component according to Claim 1 or 2, characterized in that the component comprises a bearing part, in particular bearing parts of a shaft-hub connection, of the compressor and/or the turbine of the turbo device.
4. Component according to one of Claims 1 through 3, characterized in that the titanium-aluminium alloy has a titanium portion of 40 at.% to 55 at.% and an aluminium portion of 35 at.% to 50 at.%.
5. Component according to one of Claims 1 through 4, characterized in that the component comprises a rotating blade wheel component of the compressor and/or of the turbine of the turbo device, where the component in any cross-section along its rotational axis are at least 65% or 80% of contour elements of the component symmetrical to the rotational axis of the component.
6. Component according to one of Claims 1 through 5, characterized in that the at least one additional material recess is arranged further to the outside radially, with respect to the rotational axis of the component, than the first material recess forming the bore for the bearing.
7. Component according to one of Claims 1 through 6, characterized in that the at least one additional material recess is a cavity of the component which is accessible from a component side opposite to blade elements.
8. Component according to one of Claims 1 through 7, characterized in that the at least one additional material recess is a cavity of the component which is at least partially hidden in the axial direction by an undercut of the component body, in particular by a hub component suspended from the component body.
9. Component according to one of Claims 1 through 8, characterized in that the at least one additional material recess is a cavity of the component which at least partially crosses the rotational axis of the component.
10. Component according to one of Claims 1 through 9, characterized in that the titanium-aluminium alloy contains niobium, tantalum, tungsten, zirconium and/or molybdenum, each at a proportion of 0 at.% to 11 at.%.
11. Component according to one of Claims 1 through 10, characterized in that the titanium-aluminium alloy contains iron, chromium, vanadium and/or manganese, each at a proportion of 0 at.% to 4 at.%.
12. Component according to one of Claims 1 through 11, characterized in that the titanium-aluminium alloy contains boron or carbon or silicon, each at a proportion of 0 at% to 1 at.%.
13. Component according to one of Claims 1 through 12, characterized in that the protective layer produced comprises an oxide ceramic layer, in particular an Al₂O₃ layer.
14. Component according to one of Claims 1 through 13, wherein the protective layer produced by conversion of the component surface has a thickness of 0.1 to 300 µm, in particular 1 to 10 µm.
15. Internal combustion engine with a turbo device comprising a compressor and a turbine, characterized in that the turbo device comprises at least one component according to one of the above Claims.
16. Method of manufacturing a turbo device component, in particular a component of a turbo device comprising a compressor and a turbine, according to one of Claims 1 through 14, made of a titanium-aluminium alloy having a titanium portion of 40 at.% to 60 at.% and an aluminium portion of 5 at.% to 50 at.%, or made of a titanium-aluminium alloy having a titanium portion of 40 at.% to 55 at.% and an aluminium portion of 35 at.% to 50 at.%, where on the turbo device component an aluminum oxide-containing protective layer is produced by plasma electrolytic oxidation (PEO); characterized in that this aluminium oxide-containing protective layer is produced on a surface of the turbine device component which is hidden by an undercut of the turbine device component.
17. Method according to Claim 16, characterized in that an employed electrolyte contains a silicon-containing compound as electrolyte basis at an amount of 0 - 300 g/l as well as potassium hydroxide (KOH), water glass (Na₂SiO₃), phosphoric acid (H₃PO₄), sodium phosphate (Na₃PO₄), hydrofluoric acid (HF), ammonium hydroxide (NH₄OH), boric acid (H₃BO₃), sulfuric acid (H₂SO₄), zirconium sulfate (ZrSO₄), zirconium tungstate (ZrWO₄), ammonium fluoride (NH₄F), sodium hydrogen phosphate (NaH₂PO₄), sodium fluoride diammonium hydrogen phosphate (NH₄)₂HPO₄, urea (CH₄N₂O), potassium phosphate (K₃PO₄), potassium pyrophosphate (K₄O₇P₂), dipotassium phosphate (K₂HPO₄), sodium aluminate (Na₂Al₂O₄ or NaAl(OH)₄), sodium metaaluminate (NaAlO₂), sodium fluoride (NaF), potassium fluoride (KF) and sodium hypophosphite (NaH₂PO₂) in any combination at an amount of 0 - 120 g/l each, but individually less than the electrolyte basis; as well as sodium borate (Na₂B₄O₇), ammonium hydrogen difluoride (NH₄HF₂), potassium fluorotitanate (K₂TiF₆), potassium hexafluorozirconate (K₂ZrF₆), EDTA (C₁₀H₁₂CaN₂Na₂O₈) and its salts, e.g. disodium ethylenediamine tetraacetate (Na₂H₂EDTA), tetrasodium ethylenediamine tetraacetate (Na₄EDTA) or calcium disodium ethylenediamine tetraacetate (CaNa₂EDTA), ammonium metavanadate (NH₄VO₃), disodium molybdate (Na₂MoO₄), disodium tungstate (Na₂Wo₄), hydrogen peroxide (H₂O₂), citric acid (C₆H₈O₇) as well as glycerin (C₃H₈O₃) in any combination at an amount of 0 - 20 g/l each, but individually less than the electrolyte basis, as well as urotropin at an amount of 0 - 400g/l.
18. Method according to Claims 16 or 17, characterized in that an electrolyte containing halide ions is used.
19. Method according to Claims 16 or 17, characterized in that an employed electrolyte contains a phosphorus-containing compound as electrolyte basis at an amount of 0 - 300 g/l as well as potassium hydroxide (KOH), water glass (Na₂SiO₃), phosphoric acid (H₃PO₄), sodium phosphate (Na₃PO₄), hydrofluoric acid (HF), ammonium hydroxide (NH₄OH), boric acid (H₃BO₃), sulfuric acid (H₂SO₄), zirconium sulfate (ZrSO₄), zirconium tungstate (ZrWO₄), ammonium fluoride (NH₄F), sodium hydrogen phosphate (NaH₂PO₄), sodium fluoride diammonium hydrogen phosphate (NH₄)₂HPO₄, urea (CH₄N₂O), potassium phosphate (K₃PO₄), potassium pyrophosphate (K₄O₇P₂), dipotassium phosphate (K₂HPO₄), sodium aluminate (Na2Al2O4 or NaAl(OH)₄), sodium metaaluminate (NaAlO₂), sodium fluoride (NaF), potassium fluoride (KF) and sodium hypophosphite (NaH₂PO₂) in any combination at an amount of 0 - 120 g/l each, but individually less than the electrolyte basis; as well as sodium borate (Na₂B₄O₇), ammonium hydrogen difluoride (NH₄HF₂), potassium fluorotitanate (K₂TiF₆), potassium hexafluorozirconate (K₂ZrF₆), EDTA (C₁₀H₁₂CaN₂Na₂O₈) and its salts, e. g. disodium ethylenediamine tetraacetate (Na₂H₂EDTA), tetrasodium ethylenediamine tetraacetate (Na₄EDTA) or calcium disodium ethylenediamine tetraacetate (CaNa₂EDTA), ammonium metavanadate (NH₄VO₃), disodium molybdate (Na₂MoO₄), disodium tungstate (Na₂Wo₄), hydrogen peroxide (H₂O₂), citric acid (C₆H₈O₇) as well as glycerin (C₃H₈O₃) in any combination at an amount of 0 - 20 g/l each, but individually less than the electrolyte basis, as well as urotropin at an amount of 0 - 400g/l.
20. Method according to Claims 16 or 17, characterized in that an employed electrolyte contains an aluminium-containing compound as electrolyte basis at an amount of 0 - 300 g/l as well as potassium hydroxide (KOH), water glass (Na₂SiO₃), phosphoric acid (H₃PO₄), sodium phosphate (Na₃PO₄), hydrofluoric acid (HF), ammonium hydroxide (NH₄OH), boric acid (H₃BO₃), sulfuric acid (H₂SO₄), zirconium sulfate (ZrSO₄), zirconium tungstate (ZrWO₄), ammonium fluoride (NH₄F), sodium hydrogen phosphate (NaH₂PO₄), sodium fluoride diammonium hydrogen phosphate (NH₄)₂HPO₄, urea (CH₄N₂O), potassium phosphate (K₃PO₄), potassium pyrophosphate (K₄O₇P₂), dipotassium phosphate (K₂HPO₄), sodium aluminate (Na₂Al₂O₄ or NaAl(OH)₄), sodium metaaluminate (NaAlO₂), sodium fluoride (NaF), potassium fluoride (KF) and sodium hypophosphite (NaH₂PO₂) in any combination at an amount of 0 - 120 g/l each, but individually less than the electrolyte basis; as well as sodium borate (Na₂B₄O₇), ammonium hydrogen difluoride (NH₄HF₂), potassium fluorotitanate (K₂TiF₆), potassium hexafluorozirconate (K₂ZrF₆), EDTA (C₁₀H₁₂CaN₂Na₂O₈) and its salts, e.g. disodium ethylenediamine tetraacetate (Na₂H₂EDTA), tetrasodium ethylenediamine tetraacetate (Na₄EDTA) or calcium disodium ethylenediamine tetraacetate (CaNa₂EDTA), ammonium metavanadate (NH₄VO₃), disodium molybdate (Na₂MoO₄), disodium tungstate (Na₂Wo₄), hydrogen peroxide (H₂O₂), citric acid (C₆H₈O₇) as well as glycerin (C₃H₈O₃) in any combination at an amount of 0 - 20 g/l each, but individually less than the electrolyte basis, as well as urotropin at an amount of 0 - 400g/l.
21. Method according to Claims 16 or 17, characterized in that an employed electrolyte contains a zirconium- or sulfur-containing compound as electrolyte basis at an amount of 0 - 300 g/l as well as potassium hydroxide (KOH), water glass (Na₂SiO₃), phosphoric acid (H₃PO₄), sodium phosphate (Na₃PO₄), hydrofluoric acid (HF), ammonium hydroxide (NH₄OH), boric acid (H₃BO₃), sulfuric acid (H₂SO₄), zirconium sulfate (ZrSO₄), zirconium tungstate (ZrWO₄), ammonium fluoride (NH₄F), sodium hydrogen phosphate (NaH₂PO₄), sodium fluoride diammonium hydrogen phosphate (NH₄)₂HPO₄, urea (CH₄N₂O), potassium phosphate (K₃PO₄), potassium pyrophosphate (K₄O₇P₂), dipotassium phosphate (K₂HPO₄), sodium aluminate (Na₂Al₂O₄ or NaAl(OH)₄), sodium metaaluminate (NaAlO₂), sodium fluoride (NaF), potassium fluoride (KF) and sodium hypophosphite (NaH₂PO₂) in any combination at an amount of 0 - 120 g/l each, but individually less than the electrolyte basis; as well as sodium borate (Na₂B₄O₇), ammonium hydrogen difluoride (NH₄HF₂), potassium fluorotitanate (K₂TiF₆), potassium hexafluorozirconate (K₂ZrF₆), EDTA (C₁₀H₁₂CaN₂Na₂O₈) and its salts, e.g. disodium ethylenediamine tetraacetate (Na₂H₂EDTA), tetrasodium ethylenediamine tetraacetate (Na₄EDTA) or calcium disodium ethylenediamine tetraacetate (CaNa₂EDTA), ammonium metavanadate (NH₄VO₃), disodium molybdate (Na₂MoO₄), disodium tungstate (Na₂Wo₄), hydrogen peroxide (H₂O₂), citric acid (C₆H₈O₇) as well as glycerin (C₃H₈O₃) in any combination at an amount of 0 - 20 g/l each, but individually less than the electrolyte basis, as well as urotropin at an amount of 0 - 400g/l.
22. Method according to one of Claims 16 through 21, characterized in that for conversion of the component surface, a direct current which is either constant or alternates with time, in the range of 0.1 mA to 250 A, in particular 10 mA to 120 A, or a direct voltage in the range from 10 to 1200 V, in particular from 80 V to 800 V, or an equal power in the range from 1 mW to 300 kW, in particular 8 mW to 96 kW, is used.
23. Method according to one of Claims 16 through 22, characterized in that for conversion of the component surface, a unipolar or bipolar pulse signal which is operated by current, voltage or power control and has the shape of a square-wave, a saw-tooth, a trapezoid or a half-wave or a superposition of the same, with a root-mean-square value or a peak value from 10 to 1200 V, in particular between 80 and 800 V, in voltage-controlled segments and from 0.1 mA to 250 A, in particular 10 mA to 120 A; in current-controlled segments and from 1 mW and 300 kW, in particular between 8 mW and 96 kW; in power-controlled segments with frequencies varying in time in the range from 0.01 Hz to 100 kHz, in particular from 0.1 Hz to 10 kHz, is used.
24. Method according to one of Claims 16 through 23, characterized in that for conversion of the component surface, an ideal or deformed sinusoidal signal, operated by current, voltage or power control, with any desired offset root-mean-square value or peak value from 10 to 1200 V, in particular between 80 and 800 V, in voltage-controlled segments and from 0.1 mA to 250 A, in particular 10 mA to 120A; in current-controlled segments and from 1 mW and 300kW, in particular between 8 mW and 96 kW; in power-controlled segments with frequencies varying in time in the range from 0.01 Hz to 100 kHz, in particular from 0.1 Hz to 10 kHz, is used.
25. Method according to one of Claims 16 through 21, characterized in that the electrolyte used for conversion of the component surface has a temperature range from more than or equal to 0°C to less than or equal to 100°C, in particular more than or equal to 0°C to less than or equal to 70°C.

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